How does Islam encourage unity?

Mankind was a single nation united in monotheism, then they differed. Islam is a universal religion that requires its message to be conveyed with strength based on faith and unity. Unity is an Islamic principle, and division leads to defeat. Manifestations of unity in Islam are numerous, and the hand of Allah is with the community, and congregating has been legislated in all acts of worship. Islam equates all people before the law.