Job 20:4

i.e. This which I am now about to say. How canst thou, thou, I say, who pretendest to such an exact and universal knowledge of men and things, be ignorant of so notorious a thing, which wicked men sensibly feel, and good men diligently observe, and all men are forced to acknowledge, one time or other? Of old, i.e. from the experience of all former ages. Since man was placed upon earth, i.e. since the world was made, and there were any men to observe God's government of it.