The power of the Church is spiritual, because it is given by the Holy Spirit (Acts 20:28), is a manifestation of the power of the Spirit (John 20:22-23), pertains exclusively to believers (1 Cor. 5:12-13), and can be exercised only in a spiritual way (2 Cor 10:4).
It is also a purely ministerial power, which is derived from Christ and is exercised in His name. The power of the Church is threefold:
a. A dogmatic or teaching power. The Church is commissioned to guard the truth, to hand it on faithfully from generation to generation, and to defend it against all forces of unbelief, 1Tim 1:3-4; 2Tim 1:13; Tit. 1:9-11. It must preach the Word unceasingly among all the nations of the world, Isa. 3:10-11; 2 Cor 5:20; 1Tim 4:13; 2 Tim 2:15; 4:2; Tit 2:1-10, must draw up creeds and confessions, and must provide for the training of its future ministers,
b. A governing power. God is a God of order, who desire that all things in the Church be done decently and in order, 1Cor 14:33, 40. For that reason He made provision for the proper regulation of the affairs of the Church, and gave the Church power to carry the laws of Christ into effect, John 21:15-17; Acts 20:28;
This also includes the power of discipline, Matt. 16:19; 18:18; John 20:23; 1Cor 5:2, 7, 13; 2Thess. 3:14-15; 1Tim. 1:20; Tit. 3:10. The purpose of discipline in the Church is twofold, namely, to carry into effect the law of Christ concerning the admission and exclusion of members, and to promote the spiritual edification of the members of the Church by securing their obedience to the laws of Christ. If there are diseased members, the Church will first seek to effect a cure, but if this fails will put away the diseased members. It deals with public sins even when there is no formal accusation, but in the case of private sins insists on the application of the rule laid down in Matt 18;15-18.
c. A power of ministry or mercy. Christ sent out His disciples, not only to preach, but also to heal all manner of diseases, Matt. 10;1,8; Luke 9:1-2; 10:9, 17. And among the early Christians there were some who had the gift of healing, 1Cor. 12:9-10, 28, 30. This special gift came to an end with the passing of the apostolic age. From that time on the ministry of mercy was largely limited to the Church’s care for the poor. The Lord hinted at this task in Matt. 16:11; Mark 14:7. The early Church practiced a sort of communion of goods, so than to one wanted the necessaries of life, Acts 4:34. Later on seven men were appointed to “serve the tables,” that is, to provide for a more equal distribution of what was brought for the poor, Acts 6:1-6. After that deacons are repeatedly mentioned, Romans 16:1; Phil 1:1; 1Tim. 3:8-12. Great emphasis is placed on giving or collecting for the poor, Acts 11:29; 20:35; 1Cor. 16:1-2; 2Cor 8:13-15; 9:1, 6-7; Gal 2:10; 6:10; Eph. 4:28; 1Tim. 5:10, 16; Jas 1:27; 2:15-16; 1John 3:17.
[From Berkhof Summary of Christian Doctrine]