Sahih Muslim | Book 1 | Chapter 23

Narrated by Abu Huraira
Abu Huraira reported: The Messenger of Allah (may peace and blessing be upon him) observed: You shall not enter Paradise so long as you do not affirm belief (in all those things which are the articles of faith) and you will not believe as long as you do not love one another. Should I not direct you to a thing which, if you do, will foster love amongst you: (i.e.) give currency to (the practice of paying salutation to one another by saying) as- salamu alaikum.

Narrated by Zuhair b. Harb
Zuhair b. Harb said: Jarir reported on the authority of A'mash with this chain of transmitters that the Messenger of Allah (may peace be upon him) observed: By him in Whose hand is my life, you shall not enter Paradise unless you believe. The rest of the hadith is the same as narrated by Abd Mu'awiya and Waki'.