Charles H. Spurgeon on Psalms 64:10

All the upright in heart. The word of this text, jashar, signifies rectitudinem, and planitiem, it signifies a direct way; for the devil's way was circular, compassing the earth; but the angel's way to heaven upon Jacob's ladder was a straight, a direct way. And then it signifies, as a direct and straight, so a plain, a smooth, an even way, a way that hath been beaten into a path before, a way that the fathers and the church have walked in before, and not a discovery made by our curiosity, or our confidence, in venturing from ourselves, or embracing from others, new doctrines and opinions. The persons, then, whom God proposes to be partakers of his retributions, are first, recti (that is, both direct men, and plain men), and then recti corde, this qualification, this straightness and smoothness must be in the heart; all the upright in heart shall have it. Upon this earth, a man cannot possibly make one step in a straight and a direct line. The earth itself being round, every step we make upon it must necessarily be a segment, an arc of a circle. But yet, though no piece of a circle be a straight line, yet if we take any piece, nay, if we take the whole circle, there is no corner, no angle in any place, in any entire circle. A perfect rectitude we cannot have in any way in this world; in every calling there are some inevitable temptations. But, though we cannot make up one circle of a straight line (that is impossible to human frailty), yet we may pass on without angles and corners, that is, without disguises in our religion, and without the love of craft, and falsehood, and circumvention, in our civil actions. A compass is a necessary thing in a ship, and the help of that compass brings the ship home safe, and yet that compass hath some variations, it doth not look directly north; neither is that star which we call the north pole, or by which we know the north pole, the very pole itself; but we call it so, and we make our uses of it, and our conclusions by it, as if it were so, because it is the nearest star to that pole. He that comes as near uprightness as infirmities admit, is an upright man, though he love some obliquities. John Donne.