Tosefta do Przysłów 23:36

A man may not marry a pregnant woman [who was impregnated] by his fellow, or a nursing woman [who is nursing the child] of his fellow, on account of that which is said (Prov. 23:10), "Do not remove ancient boundary stones; Do not encroach upon the field of orphans" (JPS tr.).

Originally, when the Torah would get forgotten from the Jewish people the elders would swallow it (i.e. the Torah) between themselves, [and not publicly teach it to the masses in great detail] as it is said, “And behold, Boaz was coming from Bet Lechem and he said to the harvesters, ‘Hashem is with you’. And they said to him, ‘May Hashem bless you.’” (Ruth 2:4) And [also] it says, “Hashem is with you, mighty warrior.” (Judges 6:12) And [also] it says, “… and do not scorn your mother when she has grown old.” (Proverbs 23:22)5 “It is time to do for Hashem, they have forsaken Your Torah.” (Psalms 119:126)