I heard Sulaiman bin Yasar talking about the clothes soiled with semen. He said that ʿAisha had said, "I used to wash it off the clothes of Messenger of Allah ﷺ and he would go for the prayers while water spots were still visible on them.  

عَائِشَةُ كُنْتُ أَغْسِلُهُ مِنْ ثَوْبِ رَسُولِ اللَّهِ ﷺ ثُمَّ يَخْرُجُ إِلَى الصَّلاَةِ وَأَثَرُ الْغَسْلِ فِيهِ بُقَعُ الْمَاءِ  

I used to wash the semen off the clothes of the Prophet ﷺ and even then I used to notice one or more spots on them.  

أَنَّهَا كَانَتْ تَغْسِلُ الْمَنِيَّ مِنْ ثَوْبِ النَّبِيِّ ﷺ ثُمَّ أَرَاهُ فِيهِ بُقْعَةً أَوْ بُقَعًا