Revelation 14

4 These are those who did not defile themselves with women, for they remained virgins. They follow the Lamb wherever he goes. They were purchased from among mankind and offered as first fruits to God and the Lamb. 5 No lie was found in their mouths; they are blameless.
In Old Testament, idolatry was frequently used as symbolism for spiritual separation from God. To remain spiritually pure means resisting the temptations and indulgences that the world idolises. To be one of the blameless is to stay attached to the vine such as studying scripture, participation in fellowship etc.