Contradiction with Deuteronomy 7:3
This verse commands the Israelites not to intermarry with other nations, which could contradict Genesis 25:2 where Abraham takes a wife from outside his people.
Deuteronomy 7:3: Neither shalt thou make marriages with them; thy daughter thou shalt not give unto his son, nor his daughter shalt thou take unto thy son.
Contradiction with 2 Corinthians 6:14
This verse instructs believers not to be unequally yoked with unbelievers, whereas Genesis 25:2 recounts Abraham marrying Keturah, a potential outsider.
2 Corinthians 6:14: Be ye not unequally yoked together with unbelievers: for what fellowship hath righteousness with unrighteousness? and what communion hath light with darkness?
Contradiction with Malachi 2:11
This verse condemns marrying the daughter of a foreign god, which could be seen as contradicting Abraham taking Keturah in Genesis 25:2 if she were considered an outsider.
Malachi 2:11: Judah hath dealt treacherously, and an abomination is committed in Israel and in Jerusalem; for Judah hath profaned the holiness of the LORD which he loved, and hath married the daughter of a strange god. [loved: or, ought to love]
Contradiction with Genesis 24:3-4
Abraham previously insists that Isaac should not marry a Canaanite and sends for a wife from his own people, potentially contrasting his own action in Genesis 25:2.
Genesis 24:3-4: And I will make thee swear by the LORD, the God of heaven, and the God of the earth, that thou shalt not take a wife unto my son of the daughters of the Canaanites, among whom I dwell: