A.T. Robertson Commentary Galatians 5:7

"Ye were running well; who hindered you that ye should not obey the truth?" — Galatians 5:7 (ASV)

Who did hinder you? (τις υμας ενεκοψεν?). First aorist active indicative of ενκοπτω, to cut in on one, for all the world like our use of one cutting in on us at the telephone. For this late verb see on Ac 24:4; 1 Thessalonians 2:18. Note the singular τις. There was some ringleader in the business. Some one "cut in" on the Galatians as they were running the Christian race and tried to trip them or to turn them.