Imam Ali (AS) narrated from the Prophet of Islam (PBUH) who said:

There is a container in the earth which belongs to Allah (SWT), the more pure and sincere, kinder, and stronger it is, will be more popular with God. This container is the heart of the servant of God; kind with believing brothers, strong to tell the truth, and is not afraid of the accusers and blamers; and pure and sincere means that there is no sin in it [1].

[1] Navader-e-Ravandi, Page 98.

Source: en.shafaqna.com