Abu Hazim (may Allah have mercy on him) said: I was behind Sayyiduna Abu Hurayrah (may Allah be pleased with him) while he was performing ablution for prayer. During the ablution he would extend his arm until he reached his armpit. I said to him: O Abu Hurayrah, what kind of ablution is this? He said: O Banu Farrukh, you are here? Had I known that you were here, I would not have performed this ablution. I heard my beloved friend (peace and blessings be upon him) say: "The brightness of the believer will reach as far as the water of ablution reaches."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 257