What is the ruling on urinating while standing, and is istinja’ (cleansing after defecating or urinating) obligatory for every prayer?

It is permissible to urinate while standing if one is safe from splashes, according to the hadith of Hudhayfah in the Two Sahihs. As for the hadith of Aisha forbidding it, the response is that an affirmative statement takes precedence over a negative one, or that she was recounting what she saw in her home. Istinja' (cleansing oneself after relieving oneself) is not obligatory for every prayer, but rather when its cause is present. If the discharge goes beyond its place of exit, water becomes obligatory; otherwise, istijmar (cleansing with stones or other solid objects) is permissible. There is no difference in this between men and women, except that for a thayyib (previously married) woman, if the urine extends to the exit point of menstruation, it is preferable to wash it.