Concise Theology by J.I. Packer
The eyes of the LORD are everywhere, keeping watch on the wicked and the good. PROVERBS 15:3
Omniscient is a word that means “knowing everything.” Scripture declares that God’s eyes run everywhere (Job 24:23; Pss. 33:13-15, 139:13-16; Prov. 15:3; Jer. 16:17; Heb. 4:13). He searches all hearts and observes everyone’s ways (1 Sam. 16:7; 1 Kings 8:39; 1 Chron. 28:9; Ps. 139:1-6, 23; Jer. 17:10; Luke 16:15; Rom. 8:27; Rev. 2:23)—in other words, he knows everything about everything and everybody all the time. Also, he knows the future no less than the past and the present, and possible events that never happen no less than the actual events that do (1 Sam. 23:9-13; 2 Kings 13:19; Ps. 81:14-15; Isa. 48:18). Nor does he have to “access” information about things, as a computer might retrieve a file; all his knowledge is always immediately and directly before his mind. Bible writers stand in awe of the capacity of God’s mind in this regard (Pss. 139:1-6; 147:5; Isa. 40:13-14, 28; cf. Rom. 11:33-36).
God’s knowledge is linked with his sovereignty: he knows each thing, both in itself and in relation to all other things, because he created it, sustains it, and now makes it function every moment according to his plan for it (Eph. 1:11). The idea that God could know, and foreknow, everything without controlling everything seems not only unscriptural but nonsensical.
To the Christian believer, knowledge of God’s omniscience brings the assurance that he has not been forgotten, but is being and will be cared for according to God’s promise (Isa. 40:27-31). To anyone who is not a Christian, however, the truth of God’s universal knowledge must bring dread, for it comes as a reminder that one cannot hide either oneself or one’s sins from God’s view (Pss. 139:7-12; 94:1-11; John 1:1-12).