What is the evidence for looking the place of prostration when bowing in rukoo’?

Praise be to Allah.

Firstly: 

There are ahaadeeth among the saheeh Sunnahs which mention the teaching of the Prophet (peace and blessings of Allaah be upon him) concerning looking at the place of prostration during prayer. These, in general, include all the parts of the prayer, and perhaps these texts are the ones that were quoted by the scholars of the Standing Committee and quoted by them in the answer to question no. 8580. These texts include the following: 

Ibn Hibbaan (4/332) and al-Haakim (1/625) narrated that ‘Aa’ishah said: “The Messenger of Allaah (peace and blessings of Allaah be upon him) entered the Ka’bah and his gaze did not go beyond the site of his prostration until he came out.” Classed as saheeh by al-Albaani in Sifat Salaah al-Nabi (peace and blessings of Allaah be upon him). 

With regard to the reports of some of the salaf that were quoted by ‘Abd al-Razaaq al-San’aani in al-Musannaf, these include the following: 

1 – It was narrated that Abu Qalaabah said: I asked Muslim ibn Yassaar where should my gaze fall whilst I am praying? He said: If it falls where you prostrate, that is good. 

2 – It was narrated that Ibraaheem al-Nakha’i used to like for the worshipper not to let his gaze wander beyond the place of prostration. 

3 – It was narrated that Ibn Sireen used to like for a man to focus his gaze on the place of prostration. 

Musannaf ‘Abd al-Razzaaq, 2/163 

This is what the scholars of the Standing Committee said is the view of the majority: Abu Haneefah, al-Shaafa’i and Ahmad. Some of them made an exception in the case of the tashahhud, when the worshipper should look at his finger. This is a sound exception, supported by reports in the saheeh Sunnah. 

It was narrated from ‘Abd-Allaah ibn al-Zubayr that when the Prophet (peace and blessings of Allaah be upon him) “sat for the Tashahhud, he would place his left hand on his left thigh and point with his index finger, and would not let his gaze go beyond his finger.”  

Narrated by Abu Dawood, 990; al-Nasaa’i, 1275; classed as saheeh by al-Nawawi in Sharh Muslim. 5/81. He said: The Sunnah is not to let one's gaze go beyond the pointing (finger). There is a saheeh hadeeth concerning this in Sunan Abi Dawood.  

Some of the scholars interpreted the verse in which Allaah says (interpretation of the meaning): 

“so turn your face in the direction of Al-Masjid Al-Haraam (at Makkah)”

[al-Baqarah 2:144]

as meaning that the worshipper should look straight ahead, not at the place where he prostrates, but this is a less correct view. 

Ibn Qudaamah said:  

It is mustahabb for the worshipper to fix his gaze on the place of prostration. Ahmad said – according to the report of Hanbal – : Proper focus and humility (khushoo’) in prayer means that (the worshipper) should fix his gaze on the place of prostration, this was narrated from Muslim ibn Yasaar and Qataadah. 

Al-Mughni, 1/370 

Secondly: 

In the saheeh Sunnah it is narrated that when the worshipper bows, it is mustahabb for him not to raise his head or his gaze, rather they should be level with his back. It was narrated that ‘Aa’ishah said: The Messenger of Allaah (peace and blessings of Allaah be upon him) used to start his prayer with takbeer (saying Allaahu akbar), then he would recite al-hamdu Lillaahi Rabb il-‘Aalameen (i.e., al-Faatihah), and when he bowed he would not raise or lower his head, rather it was somewhere between the two.”  

Narrated by Muslim, 498. 

Shaykh Ibn ‘Uthaymeen said, when he was explaining how rukoo’ is to be done, that it is mustahabb for the person who is bowing to keep his back in a straight line. 

He said: With his back straight means that his back should be kept straight throughout, when going down and when coming up; he should not arch his back, or bend it in such a way that the middle comes down. Rather his back should be straight. This is what has been narrated from the Prophet (peace and blessings of Allaah be upon him). ‘Aa’ishah said: “When he bowed, he did not either raise or lower his head,” – i.e., it was somewhere in between the two. 

Al-Sharh al-Mumti’, 3/90.