Charles H. Spurgeon on Psalms 49:11

Their inward thought. If good thoughts be thy deep thoughts, if, as we say, the best be at the bottom, thy thoughts are then right, and thou art righteous; for as the deep thoughts of worldlings are worldly thoughts, and the deep thoughts of wicked men are wicked thoughts, so the deep thoughts of good men are good thoughts. It is a notable observation of the Holy Ghost's concerning worldly men, that their inward thought is that their houses shall continue for ever, etc. Why? is there any thought that is not an inward thought? No, but the meaning is, though they have some floating thoughts of their mortality, and the vanity and transitoriness of all worldly things, swimming, as it were, on the top; yet they do not suffer such thoughts to sink into their hearts, or to go to the bottom; but the thoughts that lodge there are such as his, who is said by our Saviour to have thought within himself, "Soul, thou hast much goods laid up for many years; take thine ease, eat, drink, and be merry." Lu 12:19. Note the phrase, "he thought within himself." There are other kinds of thoughts that sometimes knock at the door of the worldling's heart, nay, sometimes look in at his windows, as Paul's sermon began to press in upon Felix his heart, and to set him trembling; but there are other thoughts within, which if they cannot keep good thoughts quite out, they will keep them off from making any due or deep impression upon the heart. Now, these thoughts that nestle themselves as it were at the very heart roots, to keep others out from reaching thither, these deep thoughts are they which the Scriptures call the inward thoughts, according to that of the psalmist Ps 64:6, "The inward thought of every one of them and the heart, is deep." Faithful Teat in "Right Thoughts the Righteous man's Evidence," 1666.