Acts 8:5

‘And Philip went down to the city of Samaria, and proclaimed to them the Christ.'

‘He proclaimed to them the Christ.' The spread of the Good News went further than Judaea, it reached into Samaria. Such an action would have Jesus' seal of approval on it as all knew (John 4). While Jews might avoid the Samaritans, Jesus had made quite clear that they should be welcomed under the Kingly Rule of God. So Philip boldly went among them proclaiming that the Messiah had come, and calling on them to respond to Him, thus fulfilling the command in Acts 1:8.

‘The city of Samaria.' It is not quite certain what city this involves. It was almost certainly not Sebaste, the very Romanised capital city of the region filled with foreigners. It might have been Sychar which Jesus had evangelised (John 4) with the article pointing to the city known from Christian tradition, or it may have been Shechem, where the Samaritans were centred, or it may be just be a vague description indicating that he preached in Samaritan cities.