Contradiction with Galatians 3:28
This verse states there is neither Jew nor Greek, bond nor free, male nor female in Christ Jesus, contradicting the distinction from common people in making a special vow in Numbers 6:2.
Galatians 3:28: There is neither Jew nor Greek, there is neither bond nor free, there is neither male nor female: for ye are all one in Christ Jesus.
Contradiction with Colossians 2:16
This verse states that no one should judge in matters of religious practices, which contrasts with the specific instructions in Numbers 6:2 about the Nazirite vow.
Colossians 2:16: Let no man therefore judge you in meat, or in drink, or in respect of an holyday, or of the new moon, or of the sabbath [days]: [in meat...: or, for eating and drinking] [respect: or, part]
Contradiction with Matthew 5:33-37
These verses discourage taking oaths or vows, in contrast to the vow described in Numbers 6:2.
Matthew 5:33-37: Again, ye have heard that it hath been said by them of old time, Thou shalt not forswear thyself, but shalt perform unto the Lord thine oaths: