Sunan Abi Dawud 207
Narrated Al-Miqdad ibn al-Aswad:
Ali ibn AbuTalib commanded him to ask the Messenger of Allah (ﷺ)  what a man should do when he wants to have intercourse with his wife and the prostatic fluid comes out (at this moment). (He said): I am ashamed of consulting him because of the position of his daughter. Al-Miqdad said: I asked the Messenger of Allah (ﷺ) about it.  He said: When any of you finds, he should wash his private part, and perform ablution as he does for prayer.
حَدَّثَنَا عَبْدُ اللَّهِ بْنُ مَسْلَمَةَ، عَنْ مَالِكٍ، عَنْ أَبِي النَّضْرِ، عَنْ سُلَيْمَانَ بْنِ يَسَارٍ، عَنِ الْمِقْدَادِ بْنِ الأَسْوَدِ، أَنَّ عَلِيَّ بْنَ أَبِي طَالِبٍ، - رضى الله عنه - أَمَرَهُ أَنْ يَسْأَلَ لَهُ رَسُولَ اللَّهِ صلى الله عليه وسلم عَنِ الرَّجُلِ إِذَا دَنَا مِنْ أَهْلِهِ فَخَرَجَ مِنْهُ الْمَذْىُ مَاذَا عَلَيْهِ فَإِنَّ عِنْدِي ابْنَتَهُ وَأَنَا أَسْتَحْيِي أَنْ أَسْأَلَهُ ‏.‏ قَالَ الْمِقْدَادُ فَسَأَلْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم عَنْ ذَلِكَ فَقَالَ ‏
"‏ إِذَا وَجَدَ أَحَدُكُمْ ذَلِكَ فَلْيَنْضَحْ فَرْجَهُ وَلْيَتَوَضَّأْ وُضُوءَهُ لِلصَّلاَةِ ‏"‏ ‏.‏