Jewish Babylonian Talmud – Tract Pesachim – Regulations concerning the Second Passover, the Passover at the exodus from Egypt, concerning cases where the Paschal sacrifice had become mixed.
p. 191 CHAPTER IX REGULATIONS CONCERNING THE SECOND PASSOVER--THE PASSOVER AT THE EXODUS FROM EGYPT--CONCERNING CASES WHERE THE PASCHAL SACRIFICE HAD BECOME MIXED. MISHNA: Persons who, in consequence of being (ritually) unclean or on a distant journey, did not observe the first Passover, must observe the second. Also such as have, either through error or compulsion, been prevented
