It was narrated that Az-Zuhri said: "I heard Abu Al-Ahwas saying to us in a gathering with Ibn Al-Musayyab when Ibn Al-Musayyab was sitting there, that he had heard Abu Dharr say: The Messenger of Allah (ﷺ) said: "Allah (SWT) continues to look upon His slave while he is praying, so long as he does not turn away. If he turns his face away, He turns away from him."
Source: sunnah.com
Other translations
Arabic
أَخْبَرَنَا سُوَيْدُ بْنُ نَصْرٍ، قَالَ أَنْبَأَنَا عَبْدُ اللَّهِ بْنُ الْمُبَارَكِ، عَنْ يُونُسَ، عَنِ الزُّهْرِيِّ، قَالَ سَمِعْتُ أَبَا الأَحْوَصِ، يُحَدِّثُنَا فِي مَجْلِسِ سَعِيدِ بْنِ الْمُسَيَّبِ وَابْنُ الْمُسَيَّبِ جَالِسٌ أَنَّهُ سَمِعَ أَبَا ذَرٍّ، يَقُولُ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " لاَ يَزَالُ اللَّهُ عَزَّ وَجَلَّ مُقْبِلاً عَلَى الْعَبْدِ فِي صَلاَتِهِ مَا لَمْ يَلْتَفِتْ فَإِذَا صَرَفَ وَجْهَهُ انْصَرَفَ عَنْهُ " .
sunnah.com