Albert Barnes Commentary Acts 8:25

"They therefore, when they had testified and spoken the word of the Lord, returned to Jerusalem, and preached the gospel to many villages of the Samaritans." — Acts 8:25 (ASV)

In many villages, etc. They went at first directly to the city of Samaria. On their return to Jerusalem, they travelled more at leisure, and preached in the villages also—a good example for the ministers of the gospel, and for all Christians, when travelling from place to place.

The reason why they returned to Jerusalem, and made that their permanent abode, might have been that it was important to bear witness to the resurrection of Christ in the very city where he had been crucified, and where his resurrection had occurred. If the doctrine was established there, it would be easier to establish it elsewhere.