John Gill Commentary Psalms 37:4

"Delight thyself also in Jehovah; And he will give thee the desires of thy heart." — Psalms 37:4 (ASV)

Delight yourself also in the Lord
In the persons in God, Father, Son, and Spirit; in the perfections of God, his power, goodness, faithfulness, wisdom, love, grace, and mercy; in his works of creation, providence, and redemption; in his word, his Gospel, the truths and ordinances of it; in his house, and the worship of it; and in his people, the excellent in the earth, in whom was all the delight of the psalmist; and each of these afford a field of delight and pleasure, to attend unto, contemplate, and meditate upon;

and he shall give you the desires of your heart ;
such as are according to the will of God, and for the good of his people; such as relate to communion with him, and to the communication of more grace from him, and to the enjoyment of eternal glory.