In Sermon Number 24 of Nahjul Balagha, Imam Ali (AS) advised his companions to 4 basic principles.
1. Be pious as piety is the main source of all the good.
2. Take refuge in God because there is no other refuge except Allah (SWT).
3. Take the path designated for you by Allah (SWT).
4. Perform the duties and responsibilities assigned to you by the Almighty.