Deuteronomy 25:7

And if the man like not to take his brother's wife, for the marriage was not an absolute or unavoidable duty, then let his brother's wife go up to the gate unto the elders, for questions of right and justice mere usually disposed of in the open space inside the city gates, and say, My husband's brother refuseth to raise up unto his brother a name in Israel, to perpetuate his family in the manner here provided for, he will not perform the duty of my husband's brother, namely, by marrying the widow.