A.T. Robertson Commentary Acts 11:21

"And the hand of the Lord was with them: and a great number that believed turned unto the Lord." — Acts 11:21 (ASV)

The hand of the Lord was with them (ην χειρ κυριου μετ' αυτων). This O.T. phrase (Exodus 9:3; Isaiah 59:1) is used by Luke (Luke 1:66; Acts 4:28,30; Luke 13:11). It was proof of God's approval of their course in preaching the Lord Jesus to Greeks.

Turned unto the Lord (επεστρεψεν επ τον κυριον). First aorist active indicative of επιστρεφω, common verb to turn. The usual expression for Gentiles turning to the true God (14:15; 15:3,19; 26:18,20; 1 Thessalonians 1:9). Here "Lord" refers to "the Lord Jesus" as in verse 20, though "the hand of the Lord" is the hand of Jehovah, clearly showing that the early disciples put Jesus on a par with Jehovah. His deity was not a late development read back into the early history.