It is narrated from Sayyiduna Abd al-Rahman bin Samurah (may Allah be pleased with him); he said: I know it only as being from the Prophet (peace and blessings be upon him): "Whoever performs ablution has done well, and whoever takes a ritual bath, then the ritual bath is better."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 1412