Is it obligatory to wash a garment when in doubt about it being splashed with urine after urinating while standing? And is my prayer valid if I ignore this doubt? And does the hadith about the torment of the grave due to not protecting oneself from urine apply to me? And what is meant by the saying "purity is not removed by doubt," and does this include the purity of the garment, body, and place?

A person should urinate while sitting, and it is disliked to do so while standing without an excuse. It is forbidden if one is certain that urine will splash onto their body. Hadiths have indicated the permissibility of urinating while standing. It has been said that the Prophet, peace and blessings be upon him, urinated while standing for reasons such as seeking healing for back pain, or an ailment in his hamstrings, or the absence of a suitable place to sit, or to demonstrate permissibility. One must be careful to avoid impurity because purification is a condition for the validity of prayer. Whoever does not purify themselves from urine will be tormented in their grave. As for someone who doubts whether urine has splashed onto their body or clothes, they are not obligated to perform ghusl (definition). It is preferable to wash the doubted area, because the default state is purity unless the presence of impurity is certain.