Proverbs 3:5

Trust in the Lord with all thine heart
Not in a creature, the best, the holiest, and the highest; not in any creature enjoyment, as riches, strength, and wisdom; nor in any outward privilege, arising from natural descent and education; not in a man's self, in his own heart, which is deceitful; nor in any works of righteousness done by him; not in a profession of religion, or the duties of it, ever so well performed; not in frames, nor in graces, and the exercise of them; no, not in faith or trust itself: but in the Lord, the object of all grace, and in him only; in Jehovah the Father, as the God of nature and providence, for all temporal blessings; and as the God of all grace, for all spiritual blessings, and all the needful supplies of grace; and for eternal happiness, which he has provided, promised, and freely gives. Trust in him at all times; in times of affliction, temptation, and darkness: there is a great deal of reason for it; all power and strength are in him to help; his love, grace, and mercy, move him to it, and are always the same: the consideration of what he has done for others that have trusted in him, and for ourselves in times past, should induce and encourage to it; as also the happiness of those that trust in him, who enjoy peace and safety; and his displeasure at those that show any diffidence of him, or distrust him. Trust in Jehovah the Son; in his person for acceptance; in his righteousness for justification; in his blood for pardon; in his fulness for supply; in his power for protection and preservation; and in him alone for salvation and eternal life. Trust in Jehovah the Spirit, to carry on and finish the work of grace upon the heart; of which a saint may be confident that where it is begun it will be completed. And this trust in Father, Son, and Spirit, should be "with all the heart", cordial and sincere. The phrase denotes not so much the strength of faith as the sincerity of it; it signifies a faith unfeigned; it is not saying, or professing, that a man believes and trusts in the Lord; but it is with the heart, and with his whole heart, that he believes unto righteousness, if he believes aright; see ( Romans 10:10 ) ( Acts 8:37 ) ; and lean not unto thine own understanding;
or trust not to that; for it stands opposed to trusting in the Lord. Men should not depend upon their own wisdom and understanding, in the conduct of civil life, but should seek the direction and blessing of Providence, or otherwise will meet with disappointment; and, when they succeed, should ascribe it not to their own prudence and wisdom, but to the goodness of God; for "bread" is not always "to the wise, nor riches to men of understanding", ( Ecclesiastes 9:11 ) ; and much less should men lean to their own understanding in matters of religion; a natural man has no understanding of spiritual things, of the things of the Gospel, nor indeed any practical understanding of things moral, ( Romans 3:11 ) ( 1 Corinthians 2:14 ) ( Jeremiah 4:22 ) . The understanding of man is darkened by sin; yea, is darkness itself; it is like the first earth, covered with darkness, till light is let into it, and therefore not to be leaned unto and depended on, ( Ephesians 4:18 ) ( 5:8 ) . There is a necessity of a new heart and spirit, of an understanding to be given, in order to understand spiritual and divine things, ( Ezekiel 36:26 ) ( 1 John 5:20 ) ; for though these are not contrary to the reason and understanding of men; yet they are above them, and cannot be discovered, reached, comprehended, and accounted for by them, ( Matthew 16:17 ) ( John 3:4 John 3:9 ) . Nay, there are some things in the Gospel, which, though plain to an enlightened understanding by the word of God, yet the manner how they are cannot be apprehended: as the doctrines of a trinity of Persons; of the generation of the Son of God; the procession of the Spirit; the union of the two natures in Christ; the resurrection of the dead In short, not our reason and understanding at best, and much less as carnal and unsanctified, but the word of God only is our rule of judgment, and the standard of our faith and practice; and to that we should have recourse and be directed by it, and not lean to our own understandings.