It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that Sayyiduna Abdullah bin Salam (may Allah be pleased with him) said: "O Messenger of Allah! Before you we were People of the Book, and (at that time) we were commanded to wash (after) defecation and urination." So the Prophet (peace and blessings be upon him) said: "Indeed Allah Almighty is pleased with you, He has praised you and He has loved you, so do not abandon it (this practice)."
Imam al-Tabarani (may Allah have mercy on him) said: "This hadith is narrated from Ibn Umar, from Abdullah bin Salam, only with this chain; Zuhayr bin Abbad is alone in narrating it."
Hadith Referenceالمعجم الأوسط / باب الهاء / 9363
Hadith Gradingمحدثین:إسناده ضعيف جدًّا، فيه سلام الطويل مجمع على ضعفه
Hadith Takhrij«قال الهيثمي: فيه سلام الطويل وقد أجمعوا على ضعفه «مجمع الزوائد ومنبع الفوائد، ج 1، ص 212»»