PSALM 4:8 I will both lay me down in peace, and sleep:

When a sinner is converted to God, he is said in Scripture to be united to Christ. He becomes a living member of that spiritual body of which Christ is the Head; and it is from his union with Christ that he derives all those blessings, which he enjoys now, or hopes to enjoy hereafter. In virtue of this union, he is identified, as it were, with Christ, and Christ with him; insomuch that he is represented as having died with Christ when he died, and as having risen with Christ when he arose from the dead; his sins are reckoned to Christ's account, and Christ's righteousness is imputed to him; so that, as Christ suffered his punishment, he will share in Christ's reward: he is 'a joint heir with Christ,' and has an interest in every privilege or promise which God has given to his Son on behalf of his people. The legal or judicial effect of this union is his entire justification, the pardon of his sins, the acceptance of his person, his adoption into God's family, and his final admission into heaven. And to this effect of his union with Christ the apostle refers, when he says, 'Yea doubtless, and I count all things but loss for the excellency of the knowledge of Christ Jesus my Lord; for whom I have suffered the loss of all things, and do count them but dung, that I may win Christ, and be found in him, not having mine own righteousness, which is of the law, but that which is through the faith of Christ, the righteousness which is of God by faith: that I may know him, and the power of his resurrection, and the fellowship of his sufferings, being made conformable unto his death; if by any means I might attain unto the resurrection of the dead.' But there is another effect of this union, which is equally important. By being united to Christ as a member of his spiritual body, he comes to be animated by that Spirit which pervades it, the Spirit of Christ, which is, as it were, the vital power of his body, and which actuates every member belonging to it, the Spirit with which the Head was anointed, and by reason of which he was called the Christ of God, being like the ointment which was poured on the head of Aaron, and which went down to the skirts of his garments. Every member of his body shares in this anointing, and the spiritual effect of this vital union is, that 'from Christ the Head, the whole body fitly joined together, and compacted by that which every joint supplieth, according to the effectual working in the measure of every part, maketh increase of the body unto the edifying of itself in love.' Or, as the same truth is elsewhere represented under another figure, every believer is a branch in Christ, the true vine, and from Christ derives that sap and nourishment which renders him fruitful: 'Abide in me, and I in you. As the branch cannot bear fruit of itself, except it abide in the vine; no more can ye, except ye abide in me. I am the vine, ye are the branches: he that abideth in me, and I in him, the same bringeth forth much fruit; for without,' or out of, 'me ye can do nothing.'