Although Scripture does not reveal the ultimate origin of evil, it identifies a number of intermediate sources.
Satan as a source of evil
Identified later (Rev 12:9) with Satan
pp Mk 1:13
pp Lk 4:2
See also
Satan incites David to take a census of Israel
the parable of the weeds
Satan is responsible for a woman's crippling disease
The devil prompts Judas to betray Jesus Christ
Ananias lies to the Holy Spirit at Satan's instigation
Paul's thorn in the flesh from Satan
Other evil powers
pp Mk 9:17-18
pp Lk 11:26
Fallen human nature as a source of evil
pp Mk 7:21-22
The hypocrisy of the Pharisees and teachers of the law:
pp Lk 11:39
the love of money a root of evil
The tongue is a source of evil
Physical evil is a consequence of moral evil