The  debt of gratitude and human duties to be performed and believed by  human beings towards Allahu Taala with the heart, tongue and body were  defined by Allahu Taala and communicated by His beloved Prophet  (sall-Allahu Taala alaihi wa sallam)! The human duties which Allahu  Taala showed and ordered are called Islam. One thanks Him by following  the way His Prophet taught. Allahu Taala does not accept or like any  thanks, any worship incompatible with or outside this way, because there  are many things which men consider good or beautiful but which Islam  disapproves of and regards as ugly. Hence, in thanking Allahu Taala,  people who have reasoning should adapt themselves to Hazrat Muhammad  (alaihi-salam). His way is called Islam. A person following Muhammad  (alaihi-salam) is called a Muslim. Thanking Allahu Taala, that is,  following Muhammad (alaihi-salam), is called ibada (worship).