Rubayh bin Abd al-Rahman narrates from his father, from his grandfather Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him), that the Messenger of Allah (peace and blessings be upon him) said: "There is no prayer for the one who has not performed ablution, and there is no ablution for the one who has not mentioned the name of Allah."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 192