Only found in Matt. 19:28 and Titus 3:5. This word literally means a “new birth.” The Greek word so rendered (palingenesia) is used by classical writers with reference to the changes produced by the return of spring. In Matt. 19:28 the word is equivalent to the “restitution of all things” (Acts 3:21). In Titus 3:5 it denotes that change of heart elsewhere spoken of as a passing from death to life (1 John 3:14); becoming a new creature in Christ Jesus (2 Cor. 5:17); being born again (John 3:5); a renewal of the mind (Rom. 12:2); a resurrection from the dead (Eph. 2:6); a being quickened (2:1, 5). This change is ascribed to the Holy Spirit. It originates not with man but with God (John 1:12, 13; 1 John 2:29; 5:1, 4). As to the nature of the change, it consists in the implanting of a new principle or disposition in the soul; the impartation of spiritual life to those who are by nature “dead in trespasses and sins.” The necessity of such a change is emphatically affirmed in Scripture (John 3:3; Rom. 7:18; 8:7-9; 1 Cor. 2:14; Eph. 2:1; 4:21-24).
–Easton's Bible Dictionary