Luke 20:28

Saying, master, Moses wrote unto us
In ( Deuteronomy 25:5 ) where the substance of what follows is contained, though not in express words:

if any man's brother die, having a wife, and he die without
children, that his brother should take his wife, and raise up
seed unto his brother;
the meaning of which is, that if a man died without issue, and left a wife behind him, his next brother, if unmarried, was to marry his wife, and the first child born of her, was to be reckoned the deceased's, and to inherit his estate; (See Gill on Matthew 22:24).