Sahih Muslim Book 39, Hadith Number 6744.

Ka’b reported that Allah’s Messenger (may peace be upon him) said that the similitude of a believer is that of a standing crop in a field which is shaken by wind and then it comes to its original position but it stands at its roots. The similitude of a non-believer is that of a cypress tree which stands on its roots and nothing shakes it but it is uprooted (with) one (violent stroke).