A process of making holy by separation. In the OT people and places are sanctified, i.e. reserved to the Lord, by means of sprinkling of sacrificial blood. The persistent sinfulness of the people required their ritual sanctification if they were to be the people of God's name. The Spirit of the Lord would give them a ‘new heart’ (Jer. 31: 33; Ezek. 11: 19). In the NT Jesus has been sanctified or consecrated by the Father and sent into the world (John 10: 36), and the Son has himself consecrated disciples (John 17: 17–18). But Paul teaches that for the mission to which disciples are sent, they are to live a life of sanctification (Rom. 6: 19) producing the fruit of the spirit (Gal. 5: 22–5).
In later theology, sanctification is the name given to a process which begins with baptism, continues in the life of faith supported by the sacraments, and is eventually to be completed at the final judgement (Eph. 4: 30).