Hebrews 3:12

Take heed, brethren,.... This exhortation is grounded upon the state and case of their ancestors before given, as a warning and caution to the then present Hebrews; and whom the apostle styles "brethren", to show that he had no hard thoughts of them, and that his jealousy was a godly one, and not an evil suspicion; and may teach us that all exhortations, admonitions, and reproofs should be given in love:

lest there be in any of you an evil heart of unbelief; or such an evil heart, in which unbelief prevails, and is predominant: there is in every man, whether a profane sinner, or an hypocritical professor, an evil heart, and an unbelieving one; and there is unbelief in regenerate persons, which when cherished and encouraged by them is a great evil, and should be avoided; and this sin is aggravated by the many instances of God's grace, and by the many declarations of it, and by the exceeding great and precious promises God has made, and by the great discoveries of his love to their souls in times past: and this sin, when it gets ahead, has a very great influence on the heart, to make it evil; and unbelief was the first sin of man, at least it very early appeared; it is the mother sin, and puts persons upon every sin; it defiles the conscience, hardens the heart, renders the word unprofitable, unfit for duty and makes men unstable, and therefore to be shunned; and especially because of the dreadful effect following:

in departing from the living God; that is, from Christ, who is the Son over his own house, and whose voice is to be heard; for of no other is the apostle speaking in the context; and who is not only the Son of the living God, but he is himself the living God; he is life in himself, and is the fountain and author of life, natural, spiritual, and eternal. This is mentioned to exalt the person of Christ, the apostle and high priest of our profession; and to discover the greatness and heinousness of the sin of such as depart from him and his Gospel, and to deter men from it: there is a final and total departure from Christ, from his Gospel and ordinances, from his people, and from a former profession of faith, which is never to be found in true believers; for they are as Mount Zion, which can never be removed; but there is a partial departure, and for a while, which they are liable to, and is attended with bad effects to them, and should be guarded against: saints should take heed of themselves, and of their hearts, and of the unbelief of them, that they do not in the least depart from Christ, by letting go their hold of him, or by a non-exercise of faith upon him; and this should be the care and concern of every individual member of the church, and at all times; unbelief is very dishonourable to God and Christ; contradicts the word and promises of God; is uncomfortable to the saints; it is a sin that very easily besets, and is very provoking to God, and is highly resented by him.