'Observe' in the Bible
“The Israelites are to observe the Passover at its appointed time.
You must observe it at its appointed time on the fourteenth day of this month at twilight; you are to observe it according to all its statutes and ordinances.”
But there were some men who were unclean because of a human corpse, so they could not observe the Passover on that day. These men came before Moses and Aaron the same day
“Tell the Israelites: When any one of you or your descendants is unclean because of a corpse or is on a distant journey, he may still observe the Passover to the Lord.
Such people are to observe it in the second month, on the fourteenth day at twilight. They are to eat the animal with unleavened bread and bitter herbs;
they may not leave any of it until morning or break any of its bones. They must observe the Passover according to all its statutes.
“But the man who is ceremonially clean, is not on a journey, and yet fails to observe the Passover is to be cut off from his people, because he did not present the Lord’s offering at its appointed time. That man will bear the consequences of his sin.
“If a foreigner resides with you and wants to observe the Passover to the Lord, he is to do so according to the Passover statute and its ordinances. You are to apply the same statute to both the foreign resident and the native of the land.”