This Bible contradiction is from the EvilBible.com.
A man may marry his brother's widow
Deuteronomy 25:5 View context
If brethren dwell together, and one of them die, and have no child, the wife of the dead shall not marry without unto a stranger: her husband's brother shall go in unto her, and take her to him to wife, and perform the duty of an husband's brother unto her.
A man may not marry his brother's widow
Leviticus 20:21 View context
And if a man shall take his brother's wife, it [is] an unclean thing: he hath uncovered his brother's nakedness; they shall be childless.