Why does the waiting period (iddah) for a woman whose husband has died differ from that of a woman divorced with an irrevocable major divorce?

We must understand that behind every command ordained by Allah, there is profound wisdom, and our inability to perceive it does not negate its existence. The 'iddah (waiting period) in its various forms contains the wisdom of verifying the purity of the womb to prevent the mixing of lineages, in addition to being an act of worship.

As for the 'iddah of a woman whose husband has died, which is four months and ten days, its wisdom is to honor the husband's right and to verify the purity of the womb. This duration was specified because the four months cover the period during which the soul is breathed into the fetus, and the ten days were added for the clear manifestation of movement. It is also approximately half the usual gestation period, which allows for pregnancy to become clearly evident. As for divorce, since the husband is present, the 'iddah sufficed with the 'aqra' (periods of purity/menstruation), which the woman is uniquely knowledgeable about and entrusted with.