It is reported on the authority of Ibn 'Umar that the Messenger of Allah (may peace and blessings be upon him) said:Any person who called his brother: "O unbeliever" (has in fact done an act by which this unbelief) would return to one of them. If it were so, as he asserted (then the unbelief of man was confirmed but if it was not true), then it returned to him (to the man who labeled it on his brother Muslim)
Opening the collection...
“Read in the name of your Lord who created.” 96:1
“My Lord, increase me in knowledge.” 20:114
“So remember Me; I will remember you.” 2:152
“Indeed, with hardship comes ease.” 94:6