Albert Barnes on Acts 16:4

And as they went through the cities. The cities of Syria, Cilicia, etc.

They delivered them. Paul and Silas delivered to the Christians in those cities.

The decrees. ταδογματα. The decrees in regard to the four things specified in Acts 15:20,29. The word translated decrees occurs in Lk 2:1, "A decree from Caesar Augustus;" in Acts 17:7, "The decrees of Caesar;" in Eph 2:15 and in Col 2:14. It properly means, a law or edict of a king or legislature. In this instance it was the decision of the council in a case submitted to it; and implied an obligation on the Christians to submit to that decision. The laws of the apostles would, and ought to be, in such cases, esteemed to be binding. It is probable that a correct and attested copy of the letter, Acts 15:23-29 would be sent to the various churches of the Gentiles.

To keep. To obey, or to observe.

That were ordained. Gr., That were adjudged, or determined.