Imam Abu Ya'la recorded this narration on the authority of Sayyiduna Abu Hurayrah (may Allah be pleased with him): When Thumamah bin Uthal accepted Islam, the Prophet (peace and blessings be upon him) ordered him to take a ritual bath (ghusl) and pray two rak'ahs.
The chain of Imam Ahmad and Imam al-Bazzar contains a narrator, Abdullah bin Umar al-Umari, whom Yahya bin Ma'in and Abu Ahmad bin Adi declared "thiqah (trustworthy)"; others besides these two declared him "da'if (weak)", but without attributing lying to him. Imam Abu Ya'la said (in his chain): from a man, from Sa'id al-Maqburi. (Al-Haythami says:) If he is al-Umari, then the hadith is hasan (good); and Allah knows best.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الطهارة / 1561