Deuteronomy 25:6
And it shall be, that the firstborn which she beareth shall succeed in the name of his brother which is dead, that his name be not put out of Israel. And it shall be, that the firstborn which she beareth shall succeed in the name of his brother which is dead, that his name be not put out of Israel.
The law provided that if a married man died without children, his surviving brother was to marry the widow and raise up offspring to continue the dead brother's name, so that his name would not be blotted out in Israel. Those who denied the resurrection and rejected any future rewards or punishments seized upon this provision to argue against the resurrection. They invented the case of seven brothers who in turn each married the same childless widow, and then demanded whose wife she would be when the dead rise.
Their aim in pressing that supposed difficulty was to entangle Christ in His words and to confuse other minds. By heaping ridicule upon this law they sought to bring all the Mosaic institutions into contempt. The answer given to that challenge exposed the question as resting on a false foundation. It charged those who asked it with knowing neither the Scriptures nor the power of God.