Is it sufficient to sprinkle water on the urine of a child who feeds on milk and herbs to purify the bed and mattress (including the cotton or sponge inside them), and does the same ruling apply to madhy (pre-seminal fluid) that gets on the mattress?

The bedding does not need to be purified unless one intends to pray on it. If the outer surface of the bedding becomes impure, and the impurity has not reached its inner part, then it is not considered impure merely based on doubt.

To purify impure bedding: the urine should be absorbed with a sponge, then water should be poured over the spot of impurity two or three times until it is purified.

If the impurity reaches the inner part of the bedding (cotton or sponge): the bedding must be submerged in water until the water reaches the impurity. If this is not possible, some scholars are of the opinion that it cannot be purified. Others believe that purifying only the outer surface suffices due to the difficulty involved and to avoid financial damage.

As for the urine of a male infant: its purification is lenient if the infant does not yet eat solid food out of appetite. Please refer to Fatwa (definition) no. 42935.