Spurgeon:

Psalm 139:2
“Thou knowest my downsitting and mine uprising.”

Me thou knowest, and all that comes of me. I am observed when I quietly sit down, and marked when I resolutely rise up. My most common and casual acts, my most needful and necessary movements, are noted by thee, and thou knowest the inward thoughts which regulate them. Whether I sink in lowly self-renunciation, or ascend in pride, thou seest the motions of my mind, as well as those of my body. This is a fact to be remembered every moment: sitting down to consider, or rising up to act, we are still seen, known, and read by Jehovah our Lord.

“Thou understandest my thought afar off.”

Before it is my own it is foreknown and comprehended by thee. Though my thought be invisible to the sight, though as yet I be not myself cognizant of the shape it is assuming, yet thou hast it under thy consideration, and thou perceivest its nature, its source, its drift, its result. Never dost thou misjudge or wrongly interpret me, my inmost thought is perfectly understood by thine impartial mind. Though thou shouldst give but a glance at my heart, and see me as one sees a passing meteor moving afar, yet thou wouldst by that g!impse sum up all the meanings of my soul, so transparent is everything to thy piercing glance.

Psalm 139:7
“Whither shall I go from thy spirit?”

Here omnipresence is the theme, – a truth to which omniscience naturally leads up. Not that the Psalmist wished to go from God, or to avoid the power of the divine life; but he asks this question to set forth the fact that no one can escape from the all-pervading being and observation of the Great Invisible Spirit. Observe how the writer makes the matter personal to himself – “Whither shall I go?” It were well if we all thus applied truth to our own cases. It were wise for each one to say – The spirit of the Lord is ever around me: Jehovah is omnipresent to me.