Musar sur Le Deutéronome 7:14

The Rekanati sees in our verse an allusion to the סוד העבור, the secret dimension of the mysteries of who is born, when, and to whom. The morning benediction thanking the Lord that He has not created us as a woman contains the profound allusion to the importance of not exchanging a female soul for a male one or vice versa at the time when they are reincarnated. The same Rekanati in his commentary on פרשת בראשית, writes that the secret of barrenness and inability to sire children is also due to the interchanging of male and female souls, or rather, souls from the female domain with souls from the male domain. Procreation is possible only if each of the souls of the partners involved have emanated from their respective domains, i.e. bodies and souls must match. This is why the Torah says in Deut. 7,14: לא יהיה בך עקר ועקרה -- ובהמתך, "There will be neither a male nor a female sterile person amongst you—nor amongst your livestock."