19:1 glory of God. The “glory of God,” expounded by the heavens, is not only the infinite power, variety and complexity seen in the stars but also the Lord Jesus Christ, “the brightness of His glory” (Hebrews 1:3). The “signs” established in the stars by God (Genesis 1:14) when He arranged the constellations (Job 38:31-33; etc.) originally set forth pictorially the divine plan of redemption through the coming “seed of the woman” (Genesis 3:15).
19:2 sheweth knowledge. The message goes forth through all space (Psalm 19:1) and all time (Psalm 19:2), even though there is no speech or language through which the message is conveyed (the word “where” is not in the original—Psalm 19:3).
19:4 Their line. This refers to the surveyor’s “line,” that is, the physical creation, which is everything in space and time. God’s creation is the standard against which all men are measured. The heavens declare the glory of God, but all come short of the glory of God (Romans 3:23). See also Romans 1:20, which tells us that if men fail to see the Creator through His creation, they are “without excuse.”