Exodus 13:1-3

And Jehovah spake unto Moses, saying, Sanctify unto me all the first-born, whatsoever openeth the womb among the children of Israel, both of man and of beast: it is mine. And Moses said unto the people, Remember this day, in which ye came out from Egypt, out of the house of bondage; for by strength of hand Jehovah brought you out from this place: there shall no leavened bread be eaten.