It is narrated from Sayyiduna Abdullah bin Salam (may Allah be pleased with him), who said: The Messenger of Allah (peace and blessings be upon him) came to us at the mosque whose foundation was laid on piety, that is, the Mosque of Quba. He (peace and blessings be upon him) stood at its door and said: "Allah Almighty has praised you highly regarding purification; what is your purification?" We said: "O Messenger of Allah, we are people of the Scriptures, and we find written (in our scripture) that we must cleanse ourselves (istinja) with water, and we do so to this day." He (peace and blessings be upon him) said: "Indeed, Allah Almighty has praised you highly regarding purification, for Allah said: 'Therein are men who love to purify themselves, and Allah loves those who purify themselves.'" [Surah al-Tawbah: 108]
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13979