Abdur-Razzaq عبد الرزاق بن همام · The Book Of Faith and its Signs

A man said to him: "Why don't you go out and fight?" He said: "I heard the Messenger of Allah say: 'Islam is built on five (pillars): Testimony that there is none worthy of worship except Allah, establishing Salah, giving Zakah, Hajj, and fasting Ramadan.'"

The Prophet said: "None of you has believed until he loves for his brother what he loves for himself."