Genesis: 2:18 – And the Lord God said, “It is not good that man is alone; I shall make him a helpmate opposite him.”
Gemora Hulin: 61(b): Rav Nachman said in the name of Shmuel: Even though a man may [already] have children, it is still forbidden for him to be without a wife as the verse says, “it is not good that man is alone.”
Torah Temimah – Colloquial translation of Note #40
It appears that the language of the verse [itself] is not alluding to a prohibition but rather a general suggestion. However, since the suggestion is from God, Himself, it became afterwards a [positive] commandment.
[Let’s delve deeper into the phrase] that it is “not good for man to be alone, I shall make him a helpmate…” This phrase would imply that the [whole] purpose of creation of woman is only because it is not good for him to be alone. [But] isn’t it true that, actually, in order for the world to survive there needs to be a renewal of generations? And people are like the grass of the field, “these flourish and these whither” (Gemora Eruvin: 54(a))
If so, then the purpose of creation of woman is for the necessity of the creation [and maintenance] of mankind and needed in order to be fruitful and multiply.
The answer is that the intent of this commandment is that a man and a woman should be set aside especially for each other. They should not be fruitful and multiply in a general way [with just anyone] such as animals do. Animals do not have the behavior of marriage nor any special relationship to their offspring; rather they live just according to their instincts.
Translator Note: I think that in this note the Torah Temimah is making several different points. First of all, he is emphasizing that it is not true that a woman’s role is subservient to men. Secondly, that the issue of “alone-ness” is not about man having someone to procreate with. Rather, I think the Torah Temimah is saying that the phrase “it is not good for man to be alone” is, in effect, a commandment for man and woman to have a bonding marriage. Additionally, it is worthwhile point out that is first point is that there is no prohibition in not being married, rather marriage is a positive commandment