Our Gemara on amud aleph discusses an enactment by the great Amora and Rosh Yeshiva, Rav. Even though the Torah allows for three ways to effectuate marriage, incliuding sexual intercourse with the intent to marry (Mishna KIddushin 1:1), Rav forbids a person to marry in this manner. It is considered unseemly and promiscuous.
One might wonder, what gave Rav the right to add on to the Torah’s sensibilities? If the Torah allowed this form of marriage enactment, obviously it was not considered promiscuous in the eyes of God! The answer to this has to do with a fundamental idea about certain rabbinic enactments. By way of example, let us consider Muktzeh. Do you think that Moshe Rabbenu picked up a pen or a tool on Shabbos? Of course not! Such an action would certainly violate a sense of sacredness and disrupt the meditative state of Shabbos. Moshe and his generation did not require a rabbinic enactment to reinforce a sensibility and sensitivity that was as innate as tying one’s shoe or brushing one’s teeth! Similarly, rabbinic mitzvos such as bikur holim are concretizations of pre-existing sensitivities, that at an earlier time did not require specific legislation. Likewise, we find that originally Yibum was preferred over chalitzah, but in time, the Sages doubted the person’s ability to perform the mitzvah sincerely without lustful motives. They therefore recommended Chalitzah over Yibum. The Torah didn’t change; people changed (Yevamos 39b).
Therefore, we can say that originally it was possible to carry out the legal enactment of marriage via sexual intercourse with the purest intent, so there was no need to forbid it, though perhaps the typical person had the sense of propriety to avoid this method. There is a scriptural proof to the idea that one can theoretically perform the mitzvah of marriage in the highest manner through sexual intercourse, for somoeone of great and pure spiritual stature. We find Yaakov approaching Lavan in an oddly forward manner (Bereishis 29:21):
וַיֹּ֨אמֶר יַעֲקֹ֤ב אֶל־לָבָן֙ הָבָ֣ה אֶת־אִשְׁתִּ֔י כִּ֥י מָלְא֖וּ יָמָ֑י וְאָב֖וֹאָה אֵלֶֽיהָ׃
Then Jacob said to Laban, Give me my wife, for my time is fulfilled, that I may cohabit with her.
Rashi, quoting the Midrash, comments:
For surely even the commonest of people would not use such an expression! But he said this because his mind was intent upon having issue (to fulfil his mission of rearing children who would carry on the religious traditions of his fathers) (Genesis Rabbah 70:18).
Translations Courtesy of Sefaria, except when, sometimes, I disagree with the translation 
Do you like what you see? Please subscribe and also forward any articles you enjoy to your friends, (enemies too, why not?)