The Eye Christian Symbol represents the "all-seeing eye" representing the eye of God the Father, the all-knowing and ever-present God. In later examples of Christian art the eye was pictured in a triangle with rays of light to represent the infinite holiness of the Trinity. The all seeing eye is based on the following passage in Psalm 33:18:
But the eyes of the LORD are on those who fear him, on those whose hope is in his unfailing love
The Easton Bible Dictionary provides the following definition, meaning and emblem for the Eye Christian Symbol in the Bible.
The custom of painting the eyes is alluded to in 2 Kings 9:30, R.V.; Jer. 4:30; Ezek. 23:40, a custom which still prevails extensively among Eastern women.
The expression (Prov. 23:31), "when it giveth his colour in the cup," is literally, "when it giveth out [or showeth] its eye." The beads or bubbles of wine are thus spoken of. "To set the eyes" on any one is to view him with favour (Gen. 44:21; Job 24:23; Jer. 39:12).
This word is used figuratively in the expressions an "evil eye" (Matt. 20:15), a "bountiful eye" (Prov. 22:9), "haughty eyes" (6:17 marg.), "wanton eyes" (Isa. 3:16), "eyes full of adultery" (2 Pet. 2:14), "the lust of the eyes" (1 John 2:16).
Christians are warned against "eye-service" (Eph. 6:6; Col. 3:22).
Men were sometimes punished by having their eyes put out (1 Sam. 11:2; Samson, Judg. 16:21; Zedekiah, 2 Kings 25:7).