Charles H. Spurgeon on Psalms 139:2

Afar off. Both in distance, however far off a man may seek to hide his thoughts from God; and in time, for God knows the human thought before man conceives it in his heart, in his eternal prescience. The Egyptians called God the "eye of the world." —Thomas Le Blanc.

Verses 2-4. Do not fancy that your demeanour, posture, dress, or deportment are not under God's providence. You deceive yourself. Do not think that your thoughts pass free from inspection. The Lord understands them afar off. Think not that your words are dissipated in the air before God can hear. Oh, no! He knows them even when still upon your tongue. Do not think that your ways are so private and concealed that there is none to know or censure them. You mistake. God knows all your ways. —Johann David Frisch, 1731.