[pinkpanther]

The maths was worked out by the Jewish scholars.

Now you turned to Jewish scholars? No more moslem ones?

The reasoning for that age is that Sarah, who gave birth to Isaac when she was 90, died after the binding when she was 127 years old, making Isaac around 37 at that time. Isaac was 40 years old when he married Rebecca.According to Rashi, Rebecca was 14 years old when she was married to Isaac.