The grace of God, was glad (tēn charin tēn tou theou echarē). Note repetition of the article, “the grace that of God.” The verb (second aorist passive indicative of chairō) has the same root as charis. See the same suavis paronomasia in Luk 1:28. “Grace brings gladness” (Page). “A smaller man would have raised difficulties as to circumcision or baptism” (Furneaux).
He exhorted (parekalei). Imperfect active, picturing the continuous encouragement from Barnabas.
With purpose of heart (tēi prothesei tēs kardias). Placing before (from prȯtithēmi), old word for set plan as in Act 27:13; Rom 8:28. The glow of the first enthusiasm might pass as often happens after a revival. Barnabas had a special gift (Act 4:36) for work like this.
Cleave unto the Lord (prosōmenein ̣eň tōi kuriōi). Dative case (locative if en is genuine) of kurios (here Jesus again) after prosemenein to keep on remaining loyal to (present active infinitive). Persistence was needed in such a pagan city.