The Sun does not purify

Question :

I have small children, whom I carry, and they urinate on my clothes, so I spread them out in the sun, until it is dry, then I pray in it. Is my prayer acceptable or not?

Answer:

As for the urine of a boy, it is sufficient to sprinkle it with water, if the child does not eat food, based upon the narration of Umm Qais bint Mihsan, may Allah be pleased with her. She brought her small son, who had not yet begun eating, to the Messenger of Allah and he sat him in a room, and he urinated on his garment, so he called for water and he sprinkled it, without washing it. The meaning of Nadh (the word used in the Hadith) is to wet with water, even if it does not run off onto the ground, and it does not require soaking. It is understood from this that if the baby has eaten food, the urine must be washed out. As for the urine of the girl, it must be washed out, based upon the narration of Lubabah bint Al- Harith, who said: "Al-Husain bin 'Ali was in the room of the Prophet and he urinated upon him, so I said: 'Wear another garment, and give me your Izar while I wash it.' He said:
"Only the urine of girls must be washed, and the boy's urine may be sprinkled".

This is the guidance of the Messenger regarding the ruling on the urine of the boy and the girl. From what the questioner mentioned about drying his garment in the sun on which the child has urinated and then praying in it when it is dry, it is clear that the sun does not purify it and that prayer in it is not correct, as we have said.

Source:
The Permanent Committee
Fatawa Islamiyah, Vol. 2 Pages 32-33