He came to the Prophet ﷺ and said, "I sometimes experience janabah."The Prophet ﷺ instructed him to wash his private part and perform ablution as he would for prayer.
حدثنا أبو أحمد محمد بن عبد الله حدثنا سفيان عن عبد الله بن دينار عن ابن عمر
أنه أتى النبي ﷺ فقال إنه تصيبني الجنابة فأمره أن يغسل ذكره ويتوضأ وضوءه للصلاة
Its isnad is sahih. Abu Ahmad is Muhammad bin Abdullah bin Zubayr, Abu Ahmad Zubayri, the Kufan. Sufyan is Thawri. Abdullah bin Dinar is the freedman of Ibn Umar. See 236.There is abridgment in this hadith, for he was asked about sleep after janaba, but sleep was not mentioned in this narration. See also 359.