Contradiction with John 17:15
Acts 8:5 describes Philip going to Samaria to preach, while John 17:15 implies that believers are not to be taken out of the world, suggesting remaining where they are.
John 17:15: I pray not that thou shouldest take them out of the world, but that thou shouldest keep them from the evil.
Contradiction with Matthew 10:5
Jesus instructs the disciples not to visit Samaritan towns, contradicting Philip going to Samaria in Acts 8:5.
Matthew 10:5: These twelve Jesus sent forth, and commanded them, saying, Go not into the way of the Gentiles, and into [any] city of the Samaritans enter ye not:
Contradiction with Acts 1:8
Suggests witnessing in all regions after receiving the Holy Spirit, but in Acts 8:5, Philip goes to Samaria before any mention of the Spirit being received by him.
Acts 1:8: But ye shall receive power, after that the Holy Ghost is come upon you: and ye shall be witnesses unto me both in Jerusalem, and in all Judaea, and in Samaria, and unto the uttermost part of the earth. [power...: or, the power of the Holy Ghost coming upon you]
Contradiction with Matthew 28:19
Commands making disciples of all nations, which contradicts Philip’s immediate focus only on Samaria in Acts 8:5.
Matthew 28:19: Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost: [teach...: or, make disciples, or, Christians of all nations]