A.T. Robertson Commentary Acts 15:36

"And after some days Paul said unto Barnabas, Let us return now and visit the brethren in every city wherein we proclaimed the word of the Lord, [and see] how they fare." — Acts 15:36 (ASV)

Let us return now and visit the brethren (επιστρεψαντες δε επισκεψωμεθα τους αδελφους). Paul takes the initiative as the leader, all the more so if the rebuke to Peter and Barnabas in Ga 2:11-21 had already taken place. Paul is anxious, like a true missionary, to go back to the fields where he has planted the gospel. He uses the hortatory subjunctive (επισκεψωμεθα) for the proposal (see on 15:14 for this verb). Note the repeated επ (επι- στρεψαντες and επισκεψωμεθα). There is special point in the use of δη (shortened form of ηδη), now at this juncture of affairs (cf. 13:2).

How they fare (πως εχουσιν). Indirect question, "how they have it." The precariousness of the life of new converts in pagan lands is shown in all of Paul's Epistles (Furneaux). So he wanted to go city by city (κατα πολιν πασαν).