وعن وائل بن حجر رضي الله عنه أن النبي صلى الله عليه وآله وسلم : كان إذا ركع فرج بين أصابعه وإذا سجد ضم أصابعه . رواه الحاكم.
Narrated Wa'il bin Hujr (RA): Whenever the Prophet (ﷺ) bowed, he would spread out his fingers and when he prostrated he would bring his fingers together. [Reported by al-Hakim).
Explanation & Benefits
Shaykh Safi ur-Rahman Mubarakpuri
Lexical Explanation:
«ضَمَّ أَصَابِعَهُ» would join his fingers together, meaning he would gather his fingers in such a way that they would be joined with each other and their direction would be towards the qiblah.
Benefit:
Our esteemed researcher has declared the mentioned narration weak in its chain of transmission, whereas there are supporting evidences for it in other books of hadith which are authentic. For example: In Sunan Abi Dawud, Sayyiduna Abu Humayd radi Allahu anhu narrates that when the Messenger of Allah sallallahu alayhi wa sallam would perform bowing (ruku‘), he would grasp his knees with his palms and would spread his fingers. See: [سنن ابي داود، الصلاة، حديث 731]
Similarly, in Sunan al-Kubra of al-Bayhaqi, there is also a narration supporting this issue with an authentic chain. See: [84/2، 85] And likewise, in the state of prostration (sujud), there is also mention of joining the fingers together and directing them towards the qiblah. See: [المستدرك للحاكم : 227/1، والسنن الكبريٰ للبيهقي : 112/2]
Therefore, despite the mentioned narration being weak in its chain, it is acceptable as evidence due to other supporting narrations. Thus, it is understood from this hadith that in the state of bowing (ruku‘), keeping the fingers spread is the Sunnah, and in the state of prostration (sujud), the reason for joining the fingers together is so that their direction is towards the qiblah.
Source: Bulugh al-Maram: Commentary by Safiur Rahman Mubarakpuri, Page: 237