How do we know Philip's message in Samaria was not the Gospel of grace?
Philip’s message in Samaria was not the Gospel of grace because it contained no mention of salvation through the finished work of the cross, nor of Christ’s death, burial, and resurrection for salvation. Instead, it proclaimed that the One crucified was indeed the Christ—the Gospel of the Kingdom, not yet replaced by the Gospel of grace.
Les explains that about seven years after Pentecost, after Stephen’s martyrdom, Philip—one of the seven appointed in Acts 6—went to Samaria and preached the Gospel, but not the Gospel of grace, because it had not yet been revealed. Les points out that Scripture gives no mention of salvation by the finished work of the cross, no death, burial, and resurrection for salvation. Instead, Philip’s hearers were still being told that the One they crucified was indeed the Christ. Les emphasizes that the Gospel of grace and the Gospel of the Kingdom are two distinct Good News. The Kingdom message had been going to Israel through Jesus and the twelve, and Philip continued it. Les also notes that the Samaritans who truly believed Philip’s message that Jesus was the Christ received the Holy Spirit only after Peter and John laid hands on them, showing that authority rested in Jerusalem and the twelve.