Praise be to Allah.
This hadith is jayyid and was narrated by al-Haakim in his Saheeh. The words of the Prophet (blessings and peace of Allah be upon him) are: “Avoid urine, for most of the punishment of the grave is because of it.” According to another version: “Most of the punishment of the grave is because of urine.” What it means is to avoid urine and be careful about it. If a person wants to urinate, he should urinate in a place where the surface is soft (like soil) or in a toilet, so that drops of urine will not splash back on him.
This applies to both men and women: they should pay attention to this matter. Urine should be in a place where it will not splash back on one. If some of that gets onto the thigh or foot, one should pour water on it and wash the place where it touched, so as get rid of the urine.
If the surface is soft or the individual makes sure that his urine lands in the toilet where it will be washed away when flushing, so that nothing will splash back onto him, that is sufficient.
However, avoiding urine and being careful about it is good. If it so happens that the urine hits the edge of the toilet and splashes back on the thigh or calf, then both men and women have to wash it off in that case. End quote.
Shaykh ‘Abd al-‘Azeez ibn Baz (may Allah have mercy on him)