Hadith: I used to wash the traces of semen from the garment of the Messenger of Allah (may Allah's peace and blessings be upon him) and he would go out to the prayer with water spots on his garment

عن عائشة رضي الله عنها قالت: ((كُنْت أَغْسِلُ الْجَنَابَةَ مِنْ ثَوْبِ رَسُولِ اللَّهِ صلى الله عليه وسلم فَيَخْرُجُ إلَى الصَّلاةِ، وَإِنَّ بُقَعَ الْمَاءِ فِي ثَوْبِهِ)). وَفِي رواية: ((لَقَدْ كُنْتُ أَفْرُكُهُ مِنْ ثَوْبِ رَسُولِ اللَّهِ صلى الله عليه وسلم فَرْكاً، فَيُصَلِّي فِيهِ)).
[صحيح] - [الرواية الأولى: متفق عليه. الرواية الثانية: رواها مسلم]

‘Ā'ishah (may Allah be pleased with her) reported: I used to wash the traces of semen from the garment of the Messenger of Allah (may Allah's peace and blessings be upon him) and he would go out to the prayer with water spots on his garment (i.e. before his garment is totally dry). Another narration reads: "I used to rub it well off the garment of the Messenger of Allah (may Allah's peace and blessings be upon him) and then he would pray wearing it."
[Authentic hadith] - [Narrated by Muslim - Narrated by Bukhari & Muslim]

Explanation

‘Ā'ishah (may Allah be pleased with her) mentions that when the garment of the Messenger of Allah (may Allah's peace and blessings be upon him) would become stained with semen, if it were wet, she would wash it with water and he would go out to pray wearing it while the water had not dried. If the semen were dry, she would rub it well off his garment and he would pray while wearing it.