If what was stolen is actually found alive in his possession--whether ox or donkey or sheep--he must pay back double.

Exodus 22:5
If a man grazes his livestock in a field or vineyard and allows them to stray so that they graze in someone else's field, he must make restitution from the best of his own field or vineyard.

Exodus 22:7
If a man gives his neighbor money or goods for safekeeping and they are stolen from the neighbor's house, the thief, if caught, must pay back double.

1 Samuel 12:5
Samuel said to them, "The LORD is a witness against you, and His anointed is a witness today, that you have not found anything in my hand." "He is a witness," they replied.

If the theft be certainly found in his hand alive, whether it be ox, or ass, or sheep; he shall restore double.