Qur'an 9:120
Surely, Allaah wastes not the reward of the doers of good.
(Certainly We shall not make the reward of anyone who does his (righteous) deeds in the most perfect manner to be lost)
"Verily, the believers are but a brotherhood." Qur'an 49:10
Anything that works against this feeling of brotherhood, should be avoided.
"No Muslim servant (of Allaah) prays for his brother behind his back except that an angel says, 'And for you the same.'" Recorded by Muslim
"For whoever seeks forgiveness for the believing men& women, Allaah will record one good deed corresponding to every believing man and woman." Recorded by al-Tabarani, according to al-Albani it is hasan, Sahih al-Jami