Exegesis:

ei de en daktulō theou ekballō ta daimonia ‘but if I cast out demons by the finger of God….’ The emphasis is on en daktulō theou. The accusation that Jesus casts out the demons by Beelzebul has been refuted. If it is not by Beelzebul then it must be by the finger of God.

daktulos ‘finger,’ here symbolic of God’s active power, cf. also Ex. 8.19.

ara ephthasen eph’ humas hē basileia tou theou ‘then (it is a sign that) the kingdom of God has come upon you.’ ara is inferential.

phthanō ‘to have just arrived,’ ‘to attain.’ With epi ‘upon’ it is probably a rendering of an Aramaic idiom which implies that one cannot withdraw from the meeting.

Translation:

If it is by the finger of God, an “if”-clause indicating what is not a hypothetical condition but an obvious fact, as brought out in, “no, it is rather by means of God’s power” (Good News Translation).

The finger of God. Some versions can render finger in this context literally, e.g. Kele, and Zarma (lit. ‘offspring of the hand’); elsewhere one has to shift to ‘arm,’ ‘hand’ (Dan), or to a non-metaphorical rendering such as, ‘power/strength/authority’ (Sinhala, Kituba, Ekari and several others); hence e.g. ‘through the power of God,’ and with further shifts, ‘because God’s power helps/enables me to…,’ etc., cf. on v. 15.

Then, or, ‘it-means-that’ (Sundanese), “then be sure” (New English Bible); or, if the protasis has been restructured, “which proves that” (Good News Translation), or, ‘that means that.’

The kingdom of God has come upon you, or, ‘among you all God is already ruling’ (San Miguel El Grande Mixtec).

Quoted with permission from Reiling, J. and Swellengrebel, J.L. A Handbook on the Gospel of Luke. (UBS Handbook Series). New York: UBS, 1971. For this and other handbooks for translators see here . Make sure to also consult the Handbook on the Gospel of Mark for parallel or similar verses.