It is narrated from Imam Sajjad (AS) who said: The believer has five signs:

-The believer stays away from sin, especially when no one apart from God is present.
-When the believer is in poverty, donates in the way of God as much as is able, and pays for Sadaqah.
-When the believer is inflicted with a calamity, is patient and tolerant.
-When the believer gets angry, controls himself/herself.
-When the situation is against the believer (there is a fear of loss), again he/she tells the truth [1].

[1] Beharul Anwaar, Vol. 64, Page 293.

Source: en.shafaqna.com