The Aqeedah Course by Abu Ibraheem Hussnayn

"This day, I have perfected your religion for you, completed My Favour upon you, and have chosen for you Islam as your religion." Surah Al-Ma'idah, 5. "And whoever seeks a religion other than Islam, it will never be accepted of him, and in the Hereafter he will be one of the losers." Ali-Imraan, 85. And the Messenger of Allah (sallallahu 'alayhi wa-sallam) said:

"By He in Whose Hand is my life, there is none from those who hear about me from among this Ummah, whether Jew nor Christian, and then dies without believing in me, except that he will be from the people of the Hell-fire." [Narrated by Muslim from Abu Hurayrah (radiyallahu 'anhu).]