Genesis 7:2

Of all clean. The distinction of clean and unclean beasts, appears to have been made before the law of Moses, which was not promulgated till the year of the world 2514. (Challoner). --- Clean: not according to the law of Moses, which was not yet given, but such as tradition had described --- fit for sacrifice; (Menochius) though they might be of the same species as were deemed clean in the law, which ratified the ancient institution. --- And seven: (Hebrew) simply seven, three couple and an odd female, for sacrifice after the deluge: one couple was to breed, the other two perhaps for food. (Haydock) --- Some imagine, that there were fourteen unclean and four clean animals, of every species, in the ark, because the Samaritan, Septuagint, and Vulgate read, "seven and seven." (Origen, &c.) --- But our Saviour, sending the Disciples to preach two and two, did not appoint a company of four to go together, but only of two, as is generally allowed, Mark vi. 7. (Calmet)