John Gill Bible Commentary

For my brethren and companions' sakes,.... Who were regenerated by the spirit of God; adopted into his family, and children of the same father; stood in the same relation to Christ the firstborn, and members of the same church; and so brethren: partners in the same blessings and promises of the covenant; partakers of the same grace; joined together in religious worship; shared in the same joys and griefs; travellers together to the same heavenly country, and entitled to the same glory and happiness. So David, though a king, reckoned his meanest subjects as such, who were spiritual men; and for their sakes, through the goodwill, love, and affection he bore to them, he would set praying souls an example, and by it enforce his own exhortation, as follows: I will now say, peace be within thee; now and always put up this petition, and not put it off to longer time; that peace and prosperity may always attend the church of God, as well as the city of Jerusalem, literally considered, and the inhabitants of it.