Then Zachariah prayed to his Lord saying “Lord bestow upon me from You a goodly offspring verily You are the Hearer of supplication.” That is when he saw the special gift karāma of God سبحانه with her he grew increasingly certain and ever more hopeful so he asked for a son in spite of his advanced age. The granting of his request was a rupture of ordinary reality naqḌ al-ʿāda. It is said that Zachariah عليه السلام asked for a son to help him in obedience and an heir from his progeny in prophethood so that he might uphold the right of God ḥaqq Allāh. So it was a request which deserved to be granted. When a request is for the right of the Real ḥaqq al-ḥaqq and not for the worldly concerns of the lower self ḥaẓẓ al-nafs He will not refuse it. Zachariah عليه السلام saw Mary with summer fruits in the winter and winter fruits in the summer so he asked for a son in his old age so that it might be a sign āya and a miracle muʿjiza.
