one who has not reached puberty but is close to it. Thus, if her husband has intercourse with her, even if he is an adolescent, she becomes lawful for the first husband—provided that the marriage contract is valid, as mentioned above.
“It is sufficient for the glans—or its equivalent in the case of penile amputation—to be fully inserted into her vagina with an erection, even if he does not ejaculate.” ...
His statement, “It is sufficient for the glans to be fully inserted”: the glans is the head of the penis, so the second husband must insert it in its entirety.
His statement, “or its equivalent in the case of penile amputation,” means that if it has been severed, the equivalent of the glans from what remains of the penis is sufficient. That is, complete intercourse is not required; rather, if he inserts the glans, or its equivalent in the case of penile amputation, that suffices, because thereby the tasting of sweetness is undoubtedly attained. However, complete pleasure is attained only through complete intercourse. There is no doubt that the type of intercourse he has described—namely, the full insertion of the glans—is deemed intercourse with respect to the obligation of ghusl, the establishment of lineage, the prescribed punishment for zina, and everything else consequential upon the rulings of intercourse. The scholars do not distinguish between complete penetration and otherwise, so long as the glans, or its equivalent, has been fully inserted.
His statement, “into her vagina,” is effectively repetitive of the preceding phrase, since the vagina is the front passage.
His statement, “with an erection”: erection means that the penis is erect. Thus, penetration must take place with an erection; if he penetrates without an erection, she does not become lawful to the first husband.
The apparent purport of his words is that this applies even if he ejaculates, because complete pleasure is not attained thereby. The account of Abd al-Rahman ibn al-Zubayr, may Allah be pleased with him, indicates that penetration must take place with an erection.