Despite his many excellent qualities, Isaac married late in life. God permitted him to meet the wife suitable to him only after he had successfully disproved the mocking charges of Ishmael, who was in the habit of taunting him with having been circumcised at the early age of eight days, while Ishmael had submitted himself voluntarily to the operation when he was thirteen years old. For this reason God demanded Isaac as a sacrifice when he had attained to full manhood, at the age of thirty-seven, and Isaac was ready to give up his life. Ishmael's jibes were thus robbed of their sting, and Isaac was permitted to marry. But another delay occurred before his marriage could take place. Directly after the sacrifice on Mount Moriah, his mother died, and he mourned her for three years.[3] Finally he married Rebekah, who was then a maiden of fourteen.[4] Rebekah was "a rose between thorns." Her father was the Aramean Bethuel, and her brother was Laban, but she did not walk in their ways.[5] Her piety was equal to Isaac's.[6] Nevertheless their marriage was not entirely happy, for they lived together no less than twenty years without begetting children.[7] Rebekah besought her husband to entreat God for the gift of children, as his father Abraham had done. At first Isaac would not do her bidding. God had promised Abraham a numerous progeny, and he thought their childlessness was probably Rebekah's fault, and it was her duty to supplicate God, and not his. But Rebekah would not desist, and husband and wife repaired to Mount Moriah together to pray to God there. And Isaac said: "O Lord God of heaven and earth, whose goodness and mercies fill the earth, Thou who didst take my father from his father's house and from his birthplace, and didst bring him unto this land, and didst say unto him, To thee and thy seed will I give the land, and didst promise him and declare unto him, I will multiply thy seed as the stars of heaven and as the sand of the sea, now may Thy words be verified which Thou didst speak unto my father. For Thou art the Lord our God, our eyes are toward Thee, to give us seed of men as Thou didst promise us, for Thou art the Lord our God, and our eyes are upon Thee."[8] Isaac prayed furthermore that all children destined for him might be born unto him from this pious wife of his, and Rebekah made the same petition regarding her husband Isaac and the children destined for her. Their united prayer was heard.[9] Yet it was chiefly for the sake of Isaac that God gave them children. It is true, Rebekah's piety equalled her husband's, but the prayer of a pious man who is the son of a pious man is far more efficacious than the prayer of one who, though pious himself, is descended from a godless father. The prayer wrought a great miracle, for Isaac's physique was such that he could not have been expected to beget children, and equally it was not in the course of nature that Rebekah should bear children.[10]