It is narrated from Imam Ali (AS) who said: The worst enemies of the Creator are:

1.The person who has been left alone to his/her own situation by God, and has been distanced from the right path. His/her heart loves heresy, and misleads other people, and invites them to sedition. Such a person has lost the way of the prosperity of his/her descendants, and has misled his/her current and future followers. This type of person is bearing the weight of the sins of others on his/her shoulders, and is also tangled with his/her own bad deeds.

2.The person who has fabricated some unknown topics and has found a position among ignorant people of Ummah. Such a person is sunk in darkness, and is blind to observe peace and friendship. And those who look like human being have called such a person a scholar, which in fact it is not true [1].

[1] Nahjul Balaghah, Sermon 17.