Sahih Muslim Book - 2, Hadith - 668

و حَدَّثَنَا يَحْيَى بْنُ يَحْيَى أَخْبَرَنَا خَالِدُ بْنُ عَبْدِ اللَّهِ عَنْ خَالِدٍ عَنْ أَبِي مَعْشَرٍ عَنْ إِبْرَاهِيمَ عَنْ عَلْقَمَةَ وَالْأَسْوَدِ أَنَّ رَجُلًا نَزَلَ بِعَائِشَةَ فَأَصْبَحَ يَغْسِلُ ثَوْبَهُ فَقَالَتْ عَائِشَةُ إِنَّمَا كَانَ يُجْزِئُكَ إِنْ رَأَيْتَهُ أَنْ تَغْسِلَ مَكَانَهُ فَإِنْ لَمْ تَرَ نَضَحْتَ حَوْلَهُ وَلَقَدْ رَأَيْتُنِي أَفْرُكُهُ مِنْ ثَوْبِ رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فَرْكًا فَيُصَلِّي فِيهِ.

It was narrated from 'Alqamah and Al-Aswad that a man stayed at 'Aishah's house, and in the morning he washed his garment. 'Aishah said: "It would have been sufficient, if you saw it (the semen), to wash that place, and if you did not see it, to sprinkle water around it, for I remember scratching the garment (at the place of semen) of the Messenger of Allah (s.a.w) thoroughly, then he performed Salat in it."