Does a garment become impure if it was touched by wet impurity but it left no trace?
Question

Sometimes my little girl’s garment becomes wet with impurity, then it touches my garment without me realising, but no traces of wetness appear on my garment as a result of that touching. Do I have to wash my garment in order to purify it, or is it not regarded as impure because no trace of wetness appears on it? Is there a way to purify it from impurity other than washing it, such as exposing it to sunlight, for example? Is there an age at which the infant is not impure, or is he impure from birth?
Praise be to Allah.The urine of a child is impure in all cases from birth until the end of his life, but if he is still an infant who is not yet eating solid food, there is a concession stating that the impurity is less and it is sufficient to sprinkle it with water, until the child starts to eat solid food. Once the child starts to eat solid food, his urine must be washed, because the Prophet (blessings and peace of Allah be upon him) said: “The urine of a baby boy must be sprinkled with water but the urine of a baby girl must be washed.”
What is meant is that so long as the baby boy is not yet eating solid food, there is a concession which means that the impurity is less and it must be sprinkled with water.
If the child’s garment is wet with impurity, then it touches another garment that is pure, this wetness makes the garment that it touches impure if it is wet. But if it is only slightly wet and does not affect the garment that it touches, then there is no problem and it does not become impure. But if it is clearly wet, then it will inevitably affect the garment that it touches, even if it is not visible and clear. Therefore whatever got onto the pure garment of that wetness must be washed, and you should look for where it is and wash it, and there is no way to do that except with water. Sunlight is not sufficient, and there is no alternative to washing it with water. Hence the Prophet (blessings and peace of Allah be upon him), if the urine of a boy got onto him, would pour water over it, and if the boy was very small, he did not wash it; rather it was sufficient to sprinkle water over it, as noted above. End quote.