For Jesus, the establishment of the Church was second in priority only to redeeming the world (Matt. 16:18; John 17:9). Jesus identified with the Church (Acts 9:4), declared his love for the Church (Eph. 5:25), and will one day return for his Church (Eph. 5:27; 1 Thes. 4:16). The Apostles of Christ gave their all for the establishment of the Church, nearly all being martyred for their beliefs. Paul wrote that his persecution of the Church was his most heinous crime (1 Cor. 15:9; Phil. 3:6). The Church is the body and bride of Christ (Eph. 1:22-23, 5:22-23) and the saints are the children of God (Heb.2:10-12).
The Church is both a local assembly of believers, such as the churches of Jerusalem, Ephesus, etc., as described in Acts, and the universal Church, which is comprised of all believers who have obeyed the Gospel. Each local church is a miniature version of the universal Church, with the same tenets of faith, governing structure, and ministries. A local church can be as small as 2 or 3 believers (Matt. 18:20; Col. 4:15).
The Church is part of the new covenant between God and man (Heb. 8:6-7, 13), established through Christ's blood (Heb. 9:14-15), the commandments of which are written upon the heart of each believer (2 Cor. 3:3; Heb. 8:10). There is no limitation on who may join: God calls all men to salvation (Acts17:30-31; Rom. 10:11-13; Rev. 22:17).