Sforno on Genesis 30:14/ספורנו על בראשית ל׳:י״ד

1וילך ראובן, when he saw that his mother was unhappy that she was no longer having children,

2וימצא דודאים, a pleasant smelling herb, the fragrance stimulating the human organs related to conceiving and giving birth. Our sages (Baba Kamma 82) said garlic has a similar effect on people and that this is the reason why one eats garlic on Friday nights when the husbands cohabit with their wives. The Dudaim appear to have been known as producing a similar effect. It is possible that the Dudaim had an even better effect in stimulating the feelings of love between a man and his wife. This idea is based on Song of Songs 7,13-14 שם אתן את דודי לך, הדודאים נתנו ריח, “there I will give my love to you, the mandrakes yield their fragrance.” Our verse would testify both to Reuven’s righteousness and his intelligence. especially considering that at that time he could hardly have been older than 4 or five years old.