What is the ruling regarding the spray and droplets of water mixed with urine that scatter when pouring water on the penis during Istinja'? And what should be done about purity OCD concerning mattresses that have been defiled with urine, and it is no longer possible to identify which ones they are? And does a urine stain on a mattress become purified by pouring water on it several times, knowing that the sun will later reach it?

Do not succumb to waswas (definition) (whispers of Satan, obsessive doubts). You should know that impurity on the ground is purified by pouring water over it. As long as you pour water over the impurity to remove it after relieving yourself, any splashes that come onto you after this are considered pure because the impurity has been removed.

Similarly, your act of pouring water over the spot where your elderly uncle urinated was sufficient to purify it. Therefore, walking on that spot afterwards with your foot wet or moist does no harm.

As for the carpets: If you are certain that impurity has soiled one of them, and this is not merely an illusion, and the specific carpet affected by the impurity is unknown, then its purity cannot be ascertained except by washing all these carpets. This is because the impurity is certain, and it cannot be removed except by certainty of purification. If you do not know the exact location of the impurity on the garment, you must wash the entire garment. Therefore, do not pray on any of these carpets before washing them, and this is if you are certain of the impurity.