Another matter, “when a woman conceives” – that is what is written: “I was generated in iniquity (Psalms 51:7). Rabbi Aḥa said: Even if one would be the most pious of the pious, it is impossible that he will not have one aspect of iniquity.16When engaging in marital relations, even those whose intent is to bear a child also intend to act, at least to some degree, for their own pleasure, similar to one who engages in sinful sexual activity (Maharzu).
David said before the Holy One blessed be He: ‘Master of the universe, did my father Yishai intend to produce me; was his intention not for his pleasure? Know that it is so, for after they have fulfilled their needs, this one turns his face to here and that one turns her face to there, and you insert each and every drop that is in him.’17You ensure that the semen fertilizes the ovum. That is what David said: “For my father and my mother have forsaken me, but the Lord will take me” (Psalms 27:10).
“In sin my mother conceived me” (Psalms 51:7). Rabbi Ḥiyya bar Abba said: A woman conceives only after her menstrual period and proximate to it,18Shortly after becoming pure from her menstrual impurity. The word sin [ḥet] is understood to mean purification [ḥitui], as in Leviticus 14:52 (see Nidda 31b). especially if it is a male. That is what is written: “When a woman conceives and bears a male child.”