It is impossible ( ανενδεκτον εστιν ). See  ουκ ενδεχετα in 13:33. Alpha privative ( αν- ) and  ενδεκτος, verbal adjective, from  ενδεχομα. The word occurs only in late Greek and only here in the N.T. The meaning is inadmissible, unallowable.

But that occasions of stumbling should come ( του τα σκανδαλα μη ελθειν ). This genitive articular infinitive is not easy to explain. In Ac 10:25 there is another example where the genitive articular infinitive seems to be used as a nominative (Robertson, Grammar, p. 1040). The loose Hebrew infinitive construction may have a bearing here, but one may recall that the original infinitives were either locatives ( -εν ) or datives ( -α ).  Τα σκανδαλα is simply the accusative of general reference. Literally, the not coming as to occasions of stumbling. For  σκανδαλον (a trap) see on Mt 5:29; 16:23. It is here only in Luke. The positive form of this saying appears in Mt 18:7, which see.

It were well for him ( λυσιτελε αυτω ). An old word, but only here in the N.T., from  λυσιτελης and this from  λυω, to pay, and  τα τελη, the taxes. So it pays the taxes, it returns expenses, it is profitable. Literally here, "It is profitable for him" (dative case,  αυτω ). Matthew has  συμφερε (it is advantageous, bears together for).

If a millstone were hanged ( ε λιθος μυλικος περικειτα ). Literally, "if a millstone is hanged." Present passive indicative from  περικειμα (to lie or be placed around). It is used as a perfect passive of  περιτιθημ. So it is a first-class condition, determined as fulfilled, not second-class as the English translations imply.  Μυλικος is simply a stone ( λιθος ), belonging to a mill. Here only in the text of Westcott and Hort, not in Mr 9:42 which is like Mt 18:6  μυλος ονικος where the upper millstone is turned by an ass, which see.

Were thrown ( ερριπτα ). Perfect passive indicative from  ριπτω, old verb. Literally, is thrown or has been thrown or cast or hurled. Mark has  βεβλητα and Matthew  καταποντισθη, which see, all three verbs vivid and expressive. Rather than ( η ). The comparative is not here expressed before  η as one would expect. It is implied in  λυσιτελε. See the same idiom in Lu 15:7.

If thy brother sin ( εαν αμαρτη ). Second aorist (ingressive) subjunctive in condition of third class.

Seven times in a day ( επτακις της ημερας ). Seven times within the day. On another occasion Peter's question (Mt 18:21) brought Christ's answer "seventy times seven" (verse 22), which see. Seven times during the day would be hard enough for the same offender.

Increase ( προσθες ). Second aorist active imperative of  προστιθημ, to add to. Bruce thinks that this sounds much like the stereotyped petition in church prayers. A little reflection will show that they should answer the prayer themselves.

If ye have ( ε εχετε ). Condition of the first class, assumed to be true.

Ye would say ( ελεγετε αν ). Imperfect active with  αν and so a conclusion (apodosis) of the second class, determined as unfulfilled, a mixed condition therefore.

Sycamine tree ( συκαμινω ). At the present time both the black mulberry (sycamine) and the white mulberry (sycamore) exist in Palestine. Luke alone in the N.T. uses either word, the sycamine here, the sycamore in 19:4. The distinction is not observed in the LXX, but it is observed in the late Greek medical writers for both trees have medicinal properties. Hence it may be assumed that Luke, as a physician, makes the distinction. Both trees differ from the English sycamore. In Mt 17:20 we have "mountain" in place of "sycamine tree."

Be thou rooted up ( εκριζωθητ ). First aorist passive imperative as is  φυτευθητ.

Would have obeyed ( υπηκουσεν αν ). First aorist active indicative with  αν, apodosis of a second-class condition (note aorist tense here, imperfect  ελεγετε ).

Sit down to meat ( αναπεσε ). Recline (for the meal). Literally, fall up (or back).

And will not rather say ( αλλ' ουκ ερε ).

But will not say?  Ουκ in a question expects the affirmative answer.

Gird thyself ( περιζωσαμενος ). Direct middle first aorist participle of  περιζωννυμ, to gird around.

Till I have eaten and drunken ( εως φαγω κα πιω ). More exactly, till I eat and drink. The second aorist subjunctives are not future perfects in any sense, simply punctiliar action, effective aorist.

Thou shalt eat and drink ( φαγεσα κα πιεσα ). Future middle indicative second person singular, the uncontracted forms  -εσα as often in the Koine. These futures are from the aorist stems  εφαγον and  επιον without sigma.

Does he thank? ( μη εχε χαριν; ).  Μη expects the negative answer.  Εχω χαριν, to have gratitude toward one, is an old Greek idiom (1Ti 1:12; 2Ti 1:3; Heb 12:28).

Unprofitable ( αχρειο ). The Syriac Sinaitic omits "unprofitable." The word is common in Greek literature, but in the N.T. only here and Mt 25:30 where it means "useless" ( α privative and  χρειος from  χραομα, to use). The slave who only does what he is commanded by his master to do has gained no merit or credit. "In point of fact it is not commands, but demands we have to deal with, arising out of special emergencies" (Bruce). The slavish spirit gains no promotion in business life or in the kingdom of God.

Through the midst of Samaria and Galilee ( δια μεσον Σαμαριας κα Γαλιλαιας ). This is the only instance in the N.T. of  δια with the accusative in the local sense of "through." Xenophon and Plato use  δια μεσου (genitive). Jesus was going from Ephraim (Joh 11:54) north through the midst of Samaria and Galilee so as to cross over the Jordan near Bethshean and join the Galilean caravan down through Perea to Jerusalem. The Samaritans did not object to people going north away from Jerusalem, but did not like to see them going south towards the city (Lu 9:51-56).

Which stood afar off ( ο ανεστησαν πορρωθεν ). The margin of Westcott and Hort reads simply  εστησαν. The compound read by B means "rose up," but they stood at a distance (Le 13:45f.). The first healing of a leper (5:12-16) like this is given by Luke only.

Lifted up ( ηραν ). First aorist active of the liquid verb  αιρω.

As they went ( εν τω υπαγειν αυτους ). Favourite Lukan idiom of  εν with articular infinitive as in 17:11 and often.

And he was a Samaritan ( κα αυτος ην Σαμαρειτης ). This touch colours the whole incident. The one man who felt grateful enough to come back and thank Jesus for the blessing was a despised Samaritan. The  αυτος has point here.

Save this stranger ( ε μη ο αλλογενης ). The old word was  αλλοφυλος (Ac 10:28), but  αλλογενης occurs in the LXX, Josephus, and inscriptions. Deissmann (Light from the Ancient East, p. 80) gives the inscription from the limestone block from the Temple of Israel in Jerusalem which uses this very word which may have been read by Jesus:

Let no foreigner enter within the screen and enclosure surrounding the sanctuary ( Μηθενα αλλογενη εισπορευεσθα εντος του περ το ιερον τρυφακτου κα περιβολου ).

With observation ( μετα παρατησεως ). Late Greek word from  παρατηρεω, to watch closely. Only here in the N.T. Medical writers use it of watching the symptoms of disease. It is used also of close astronomical observations. But close watching of external phenomena will not reveal the signs of the kingdom of God.

Within you ( εντος υμων ). This is the obvious, and, as I think, the necessary meaning of  εντος. The examples cited of the use of  εντος in Xenophon and Plato where  εντος means "among" do not bear that out when investigated. Field (Ot. Norv.) "contends that there is no clear instance of  εντος in the sense of among" (Bruce), and rightly so. What Jesus says to the Pharisees is that they, as others, are to look for the kingdom of God within themselves, not in outward displays and supernatural manifestations. It is not a localized display "Here" or "There." It is in this sense that in Lu 11:20 Jesus spoke of the kingdom of God as "come upon you" ( εφθασεν εφ' υμας ), speaking to Pharisees. The only other instance of  εντος in the N.T. (Mt 23:26) necessarily means "within" ("the inside of the cup"). There is, beside, the use of  εντος meaning "within" in the Oxyrhynchus Papyrus saying of Jesus of the Third Century (Deissmann, Light from the Ancient East, p. 426) which is interesting: "The kingdom of heaven is within you" ( εντος υμων as here in Lu 17:21).

Go not away nor follow after them ( μη απελθητε μηδε διωξητε ). Westcott and Hort bracket  απελθητε μηδε. Note aorist subjunctive with  μη in prohibition, ingressive aorist. Do not rush after those who set times and places for the second advent. The Messiah was already present in the first advent (verse 21) though the Pharisees did not know it.

Lighteneth ( αστραπτουσα ). An old and common verb, though only here and 24:4 in the N.T. The second coming will be sudden and universally visible. There are still some poor souls who are waiting in Jerusalem under the delusion that Jesus will come there and nowhere else.

But first ( πρωτον δε ). The second coming will be only after the Cross.

They ate, they drank, they married, they were given in marriage ( ησθιον, επινον, εγαμουν, εγαμιζοντο ). Imperfects all of them vividly picturing the life of the time of Noah. But the other tenses are aorists (Noah entered  εισηλθεν, the flood came  ηλθεν, destroyed  απωλεσεν ).

Note the same sharp contrast between the imperfects here ( ate  ησθιον,

drank  επινον,

bought  ηγοραζον,

sold  επωλουν,

planted  εφυτευον,

builded  ωικοδομουν ) and the aorists in verse 29 ( went out  εξηλθεν,

rained  εβρεξεν,

destroyed  απωλεσεν ).

Is revealed ( αποκαλυπτετα ). Prophetic and futuristic present passive indicative.

Let him not go down ( μη καταβατω ). Second aorist active imperative of  καταβαινω with  μη in a prohibition in the third person singular. The usual idiom here would be  μη and the aorist subjunctive. See Mr 13:15f.; Mt 24:17f. when these words occur in the great eschatological discussion concerning flight before the destruction of Jerusalem. Here the application is "absolute indifference to all worldly interests as the attitude of readiness for the Son of Man" (Plummer).

Remember Lot's wife ( μνημονευετε της γυναικος Λωτ ). Here only in the N.T. A pertinent illustration to warn against looking back with yearning after what has been left behind (Ge 19:26).

Shall preserve it ( ζωογονησε αυτην ). Or save it alive. Here only in the N.T. except 1Ti 6:13; Ac 7:19. It is a late word and common in medical writers, to bring forth alive ( ζωοσ, γενω ) and here to keep alive.

In that night ( ταυτη τη νυκτ ). More vivid still, "on this night," when Christ comes.

Shall be grinding ( εσοντα αληθουσα ). Periphrastic future active indicative of  αληθω, an old verb only in the N.T. here and Mt 24:41.

Together ( επ το αυτο ). In the same place, near together as in Ac 2:1.

The eagles ( ο αετο ). Or the vultures attracted by the carcass. This proverb is quoted also in Mt 24:28. See Job 39:27-30; Heb 1:8; Ho 8:1. Double compound ( επι-συν- ) in  επι-συν-αχθησοντα completes the picture.