Galatians 3:3

πνεύματι … σαρκὶ. These two datives denote the two internal spheres susceptible of moral influence. Conversion had brought about a spiritual change as its immediate result: it was folly to look for a consummation of this change from an ordinance of the flesh like circumcision. This was to exalt flesh above spirit instead of rising from flesh to spirit. ἐνάρχεσθαι and ἐπιτελεῖν are coupled together in 2 Corinthians 8:6 and Philippians 1:6 to express the beginning and consummation of works of mercy and sanctification. Greek authors use ἐνάρχεσθαι with reference to the initial ceremony of a sacrifice (Eur., Iph., A. 147, 435, 955), ἐπιτελεῖν in Hebrews 9:6 refers to the performance of ritual. The middle voice ἐπιτελεῖσθε is used here because the spiritual process is to be wrought by them upon themselves.