Deuteronomy 6:5

And thou shalt love the Lord thy God
Which is the first and chief commandment in the law, the sum and substance of the first table of it; and includes in it, or at least has connected with it, knowledge of God, esteem of him, delight in him, faith and trust in him, fear and worship of him, and obedience to him, which when right springs from it. God is to be loved because of the perfections of his nature, and the works of his hand, of nature, providence, and grace; and because of the relations he stands in to men, and especially to his own people; and because of his peculiar love to them; and, indeed, he is to be loved by all men for his care of them, and blessings of goodness bestowed on them; the manner in which this is to be done follows:

with all thine heart, and with all thy soul, and with all thy might;
with a superlative love, above all creatures whatever; with the whole of the affections of the heart, with great fervency and ardour of spirit, in the sincerity of the soul, and with all the strength of grace a man has, with such love that is as strong as death. Jarchi interprets loving God with all the heart, that is, with thy heart not divided about God, a heart not divided between God and the creature; "all thy might" he interprets of mammon or substance; and, indeed, that is one way in which men may show their love to God, by laying out their substance in his service, and for the support of his cause and interest in the world. Aben Ezra by "the heart" understands knowledge, and by the "soul" the spirit of man that is in his body, and by might perfect love in the heart.