And if a stranger shall sojourn among you, and will keep the passover unto the LORD; according to the ordinance of the passover, and according to the manner thereof, so shall he do: ye shall have one ordinance, both for the stranger, and for him that was born in the land. Numbers 9:14
At least if they're circumcised.
And when a stranger shall sojourn with thee, and will keep the passover to the LORD, let all his males be circumcised, and then let him come near and keep it; and he shall be as one that is born in the land. Exodus 12:48
And the LORD said unto Moses and Aaron, This is the ordinance of the passover: There shall no stranger eat thereof. Exodus 12:43