(a) It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "When one of you is about to prostrate, he should not kneel down as a camel kneels; rather, he should place his hands on his knees."
(b) He narrated it with the words 'ala rukbatayhi (on his knees). If this narration is sound, it is evidence that the worshipper places his hands on his knees when going down into prostration.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2634