Hüseyin Hilmi Isık "rahimehullah"

"Two people went to the mosque and prayed there. Something was offered to them. They said they were fasting. After talking for a while, when they were about to leave, the Prophet (sall-Allahu ’alaihi wa sallam) said to them: Do your prayers again, and perform your fasting again! For you have backbitten someone in your conversation. [That is, you have mentioned one of his faults.] Backbiting removes the thawab (blessings) of worships."
Hadith-i Sharif