The Duties of the Heart, by Rabbi Bachye, tr. by Edwin Collins, , at sacred-texts.com
Among commands relating to duties of the heart and mind are the following:—To believe that the world has a Creator, who created it from nothing, and that there is none other like Him. To accept His Unity and worship Him in our hearts. To devote intelligent thought to the wonders of His Creation, so that they may be to us a sign concerning Him. To trust in Him, and humble ourselves before Him; to fear Him, to tremble at the thought that He looks at us—at all that is revealed and all that is hidden about us; to desire to do His will; and to concentrate all our efforts upon good deeds that are absolutely disinterested and only motived by love of God. Further, that we should love Him and those that love Him, and hate those that hate Him.
Also, that we should not covet, and not avenge, or bear a grudge. (Compare Levit. xix.) They also forbid us to think sinful thoughts, or to have sinful desires, and even to contemplate the commission
of any transgression, and other similar things which are hidden from man and none but God, alone, can see.
Thus the duties of the heart involve the formation of ideals of conduct, love of man, faith, etc.; the cultivation of right beliefs based upon Reason; the conscious effort of the mind to realise the wonders of creation, so that we may come to know, of God, truths which human language, that can only accurately tell of things material, can never adequately express. That trust in God which makes right conduct possible, even at the cost of personal risk and loss; the banishing of hatred, envy, scorn, all longing for revenge, and all desire for sin, are also obligations of the heart. And they include all nuances of virtue, such as these that have their being in the heart alone, and are not manifested in material life, save only by their influence; and yearning, till the yearning one turns pale with longing, * to realise, in thought and mind and deed, the will of God. And chief among them is the attuning of the soul into such perfect harmony with God, that all right conduct and right thought must follow without effort on our part, because our will is one with His, through love.
19:* This is the literal translation of nichsof; comp. keseph, silver.