After people paid their allegiance to him, Imam Ali (AS) said: Swear to God who justly appointed the Prophet of Islam (PBUH), you will be tested seriously, like seeds poured in a sieve, or food which is placed in a dish. You will be displaced and turned upside down, until the low comes to top, and vice-versa. Those who have good records in Islam and so far have been sidelined will take over the affairs and those who unjustly occupied positions will be pushed back [1].
[1] Nahjul Balaghah, Sermon 16.