These are the main teachings of Islam:
1) Testify that "There is only one God and Muhammad is His messenger."
2) Pray five times a day (dawn, noon, mid-afternoon, sunset, nightfall) facing Mecca (and wash before praying.) Gather at Mosque for noon prayer and sermon on Fridays.
3) Do not eat or drink between sunrise and sunset during the lunar month of Ramadan
4) Give alms (charity) to the poor
5) If possible, go on pilgrimage to Makkah (Mecca) at least once during the first days of Dhu'l-Hijja (the twelfth month of the Muslim calendar (Hajj)
All of these helped to unify the Muslim community.