Musar zu Tehillim 15:5

Eighteenth, to make the love of God the intention of his service. And the love of God can be made complete in these four ways: by joining in companionship with the pious and the wise, by staying far away from the companionship of the wicked and the fools, by occupying himself with the words of our teachers, of blessed memory, and with holy books, and by keeping at a distance from the so-called secular wisdoms. Now, if a man accustoms himself to these four things, of him it can be said (Psalms 15:5), “He that doeth these things shall never be moved.”