(122) باب وَضْعِ الْيُمْنَى عَلَى الْيُسْرَى فِي الصَّلاَةِ
Jarir ad-Dabbi reported:
I saw Ali (Allah be pleased with him) catching hold of his left hand) by his right hand on the wrist above the navel.Abu Dawud said: Sa'id b. Jubair narrated the words: "above the navel". Abu Mijlaz reported the words: "below the navel". This has also been narrated by Abu Hurairah. But that is not strong.
Reference: Sunan Abi Dawud 757
In-book reference: Book 2, Hadith 367
English translation: Book 3, Hadith 756