Contradiction with John 3:5
Jesus states that being born of water and the Spirit is necessary for entering the kingdom of God, which suggests baptism is essential for salvation, conflicting with interpretations that Acts 8:38 implies only belief is needed.
John 3:5: Jesus answered, Verily, verily, I say unto thee, Except a man be born of water and [of] the Spirit, he cannot enter into the kingdom of God.
Contradiction with 1 Corinthians 1:17
Paul claims Christ did not send him to baptize but to preach the gospel, indicating baptism may not be as central as Acts 8:38 implies through the eunuch's immediate baptism.
1 Corinthians 1:17: For Christ sent me not to baptize, but to preach the gospel: not with wisdom of words, lest the cross of Christ should be made of none effect. [words: or, speech]
Contradiction with Acts 10:44-48
Cornelius and his household receive the Holy Spirit before being baptized, suggesting the sequence in Acts 8:38 might not be necessary, where baptism follows belief right away.
Acts 10:44-48: While Peter yet spake these words, the Holy Ghost fell on all them which heard the word.