We learn from Rabbi Aba that when God completed the world below, He wished to complete the body of man with the soul, so He created him male and female. Only when a man joins with his wife and they have a son and daughter is man complete in the likeness of above. If a man does not have children his soul does not join the Holy Name when he dies. Rabbi Aba tells us that "a priest's daughter" is the holy soul, because it issued from the union of Zeir Anpin and Malchut. He adds that "no stranger shall eat of it" means that anyone who did not have children will not be able to partake of the supernal delight in God.