In The Name of Allaah, The Most Merciful, The Bestower of Mercy.

• He said to the people after becoming the Khaleefah, “I command you to fear Allaah, because fear of Allaah precedes everything and nothing precedes it. Remember death a lot, because indeed it is the destroyer of pleasures and  prepare for it properly before it arrives. Indeed, the Ummah does not differ that Allaah is their Lord, the Qur’aan is their Book and that Muhammad is their Prophet, but they differ in matters of the worldly life and wealth. By Allaah! Neither will I give anyone based on falsehood nor deprive anyone of his rights”. Then he raised his voice and said, “O people! It is obligatory to obey whoever obeys Allaah and whoever disobeys Allaah is not to be obeyed. Obey me as long as I obey Allaah, but do not obey me if I disobey Allaah”. [End of quote]
• [NB: Although rulers are not obeyed in disobedience to Allaah, but neither are they rebelled against nor is rebellion incited against them. read here: https://www.abukhadeejah.com/the-tyranny-of-the-rulers-a-reason-for-rebellion/]

• He once wrote to one of his officials and said, “Indeed, I command you to fear Allaah, adhere to the Sunnah of Allaah’s Messenger, limit yourself to the Messenger’s command, abandon that which the people have newly initiated in the religion after him – those who wage war against the Sunnah –  and have stopped acting on his true religion. Know that an innovation in religious affairs has never occurred, except that there is evidence to show its falsity, therefore it is obligated on you to adhere to the Sunnah, for indeed it is the tradition of those [i.e. the Sahaabah] who know the deviation, error and  foolishness that is in that which is in opposition to it. They were more able to explain the affairs and more robust in the performance of deeds. Their deeds were performed properly, therefore if that which you do is virtuous, they would have been foremost in doing so, because they preceded everyone in every good. And if you say, “Good has also occurred after them”, then know that it was initiated by one who followed other than the path of the believers- deviated from their path and turned himself away from it. Indeed, they [i.e. Sahaabah] have spoken about the [religious innovations] based on that which suffices and described it with that which solves the problem, so those who do not act based on what they followed have fallen short and those who go beyond what they followed are not good doers. Indeed, a people diminished their religion and became mixed up and others wanted to go above them and became extremists.
• He said, “Allaah’s Messenger and his Khulafaa after him established Sunan, adhering to it is obedience to Allaah and a testification that the Book of Allaah is truth. It is not allowed for anyone to change or substitute it and no consideration is given to anyone who opposes it. Whoever adheres to that which has preceded will be guided and the one who uses it as a source of foresight will be able to see clearly. As for the one who opposes it and follows other than the path of the believers, Allaah will leave him in the path he has chosen and burn him in hell, and what an evil destination!”.

• One day, he spoke in the presence of a group of his companions and Allaah granted him the ability to convey a fine admonition, then he saw a man in the gathering whose eyes were filled with tears, so he immediately stopped talking. The man said to him, “O Ameerul Mumineen! Carry on with your admonition because indeed I hope that Allaah will bless the one who hears or the one it reaches”. He said to the man, “O Abu Ayyoub! Take this from me, for indeed there is trial whose evil the speaker may not escape when speaking to the people. Acting is more appropriate for the believer than speaking”.

• Rajaa said, “When Umar Bin Abdul Azeez was about to depart from this world, he kept on saying, “O Allaah! Make me pleased with your divine will and bless me in your divine decree, so that I do not hasten what you have delayed and not delay what you have hastened”.

Excerpt from Al-Bidaayah Wan Nihaayah. Vol 9. pages 213–217. Slightly paraphrased. Publisher: Maktabah Al-Ma’aarif and Daar ibn Hazm. 9th Edition. 1414 AH (1994)