It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) concerning a man who has a wet dream (emission in sleep) in his garment and then the place of the impurity becomes hidden from him (that is, he cannot tell where the impurity is), that he said: "Wash the entire garment."
Its chain contains an unnamed (unknown) narrator, because of which this narration is technically weak.
Hadith Referenceالمطالب العالية بزوائد المسانيد الثمانية / كتاب الغسل / 185
Hadith Gradingمحدثین:إسناده صحيح، موقوف
Hadith Takhrij«حکم الحدیث المطالب العالیہ محققاً تنسیق د. سعد بن ناصر بن عبد العزيز الشَّثري- مکتبہ شاملہ :موقوف، إسناده صحيح. » «انفرد به المصنف من هذا الطريق»