Tafsir of Ash-Shu`ara' 26:219

And your movements among those who fall prostrate. Qatadah said:

الذي يراك حين تقوم

وتقلبك في الساجدين

Who sees you when you stand up. And your movements among those who fall prostrate. "When you pray, He sees you when you pray alone and when you pray in congregation.'' This was also the view of Ikrimah, Ata' Al-Khurasani and Al-Hasan Al-Basri

إنه هو السميع العليم