Every human is born in a state of Fitrah (divinely endowed natural disposition of monotheism/Islam). The Prophet (peace be upon him) said:
Every newborn is born in a state of Fitrah. Its parents then make it a Jew, a Christian, or a Magian.
(Agreed upon by Imams Al-Bukhari and Muslim from the Hadith of
Abu Hurayrah, may Allah be pleased with him)However, Fitrah alone is not enough to know the details of Tawhid (belief in the Oneness of Allah/monotheism) and how to worship Allah (Glorified and Exalted be He). It is incumbent to learn and try to become versed in religion; to follow and obey the Messenger of Allah (peace be upon him) who conveyed all details that Allah's Slaves need about religion and `Ibadah (worship). (Part No. 2; Page No. 35) This is the way a Muslim can know the `Ibadah for which Allah created humanity. Allah (Glorified be He) says:
And I (Allâh) created not the jinn and mankind except that they should worship Me (Alone).
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.