And it was at the end of thirty years from the making of this covenant, that Izhak was born; and thence until they went out of Mizraim four hundred (years), on the selfsame day it was that all the hosts of the Lord went forth made free from the land of Mizraim.
Isaac Was Born Thirty Years After the Covenant Between the Pieces
Targum Pseudo-Jonathan on Exodus 12:41