Prayer, Zakat, and fulfillment of obligations
Nahj al-Balāgha|Volume 1|Book 1|Chapter 199
[علم اللّه تعالى :] إِنَّ اللهَ سُبْحَانَهُ لاَ يَخْفَى عَلَيْهِ مَا الْعِبَادُ مُقْتَرِفُونَ فِي لَيْلِهِمْ وَنَهَارِهِمْ، لَطُفَ بِهِ خُبْراً، وَأَحَاطَ بِهِ عِلْماً، أَعْضَاؤُكُمْ شُهُودُهُ، وَجَوَارِحُكُمْ جُنُودُهُ، وَضَمائِرُكُمْ عُيُونُهُ، وَخَلَوَاتُكُمْ عِيَانُهُ.
Surely, Allāh, the Glorified, the Sublime, nothing is hidden from Him of whatever people do in their nights or days. He knows all the details, and His knowledge covers them. Your limbs are a witness, the organs of your body constitute an army (against yourself), your inner self serves Him as eyes (to watch your sins), and your loneliness is open to Him.