Samuel Rutherford (The Covenant of Life Opened, p. 65):
Self-searching is a reflect act upon the state (and such acts are more spirituall, then direct acts) and therefore it should be the work of all, to try, under what reign they are, whether of the first or second Adam. And whereas Angels cover their faces and their feet with wings, Isa. 6. before God and are full of eyes, as without, so also within Revel. 4:8. We may hence learn, such come nearest to the nature of these pure and heavenly Spirits, who have eyes within to see what they are, and their blacknesse of face and feet, when they compare themselves either with the Holy God, or his Holy Law. 2. The Carnall man is a beast, Psal 49:20. and beasts have no reflect acts upon their own beastly state. 3. The more of a spirituall life is in any the more stirring in communing with their own heart, the Law makes, the more of life that is in the worme when tramped on, the more stirring it makes: deadnesse and stupiditie in not being versed and well read and skilled in our selves and our own heart, argues little of the Spirit, and estrangement to a spirituall Covenant, nor can any lay hold on the Covenant of Grace in a night dream.