Abdullah bin Abbas reported,
Ali 
said, "I sent Miqdad to the Messenger of Allah ﷺ to ask him about prepatory fluid (madhi)."The Prophet ﷺ replied, "Perform ablution and wash your private part."Abu Abdul-Rahman said, "Makhramah did not hear anything directly from his father."
Nasai 439
Sahihأخبرنا أحمد بن عيسى عن ابن وهب وذكر كلمة معناها أخبرني مخرمة بن بكير عن أبيه عن سليمان بن يسار
عن ابن عباس قال
قال علي رضي الله عنه أرسلت المقداد إلى رسول الله ﷺ يسأله عن المذي فقال توضأ وانضح فرجك قال أبو عبد الرحمن مخرمة لم يسمع من أبيه شيئا
No references are available.
Muslim recorded it, hadith no. 19/303, from Ahmad bin Isa, with the same chain. See the previous hadith.Makhrama narrated from his father's book, either by authorization, by finding it in writing, or by some other means, so it can be relied upon as evidence.