Rabbi Chakhinai said: The Holy One, blessed be He, set no limit to the kingdoms, except to the Egyptian bondage, and to the kingdom of Babylon. Whence do we know this about the Egyptian bondage? Because it is said, "And they shall serve them; and they shall afflict them four hundred years" (Gen. 15:13). The Holy One, blessed be He, dealt according to the abundance of His tender mercy, and He shortened (this time limit) by its half, 210 years. Whence do we know about the Babylonian kingdom? Because it is said, "For thus saith the Lord, After seventy years be accomplished for Babylon, I will visit you, and perform my good word toward you, in causing you to return to this place" (Jer. 29:10).