In the same book, it is also related that,
According to 'Abdallaah - his father - al-Fudayl - 'Abdallaah: I was told that 'Umar bin 'Abd al Azeez wrote to the Syrian army as follows:
"As Salaamu 'alaykum wa Rahmatullaah.
Now then, whoever contemplates death frequently, speaks little, while he who knows that death is certain, is satisfied with a little.
Farewell."
According to Mansoor bin Muzaahim - Shu'ayb, that is, Ibn Safwaan - Ibn 'Abd al-Hameed: 'Umar ibn 'Abd al 'Azeez said:
"He who gives sincere advice to his brother in matters of religion and looks out for the well being of the latter's daily affairs has fulfilled his brotherly obligation, and carried out the duty that was incumbent upon him.
Ittaqillaah (Fear Allah)...
Accept these words, for they are offered as sincere advice to you with regard to your religion; and cling fast to them, for they constitute a warning that will save you in the afterlife.
The sustenance has been apportioned; therefore, let no believer exceed what has been apportioned to him, and be united in seeking the good.
In contentment there is abundance, substinence, and sufficiency.
The term of this life is in your necks, and Jahannam lies before you. What you see will pass away, what has been is as if it never was, and all will soon be dead. You have seen the stages of the dying man, both when he is in the agony of death, and then after his demise when he has tasted death and the people all around him are saying, "He has passed away, May Allah Ta'aala have mercy on his soul."
You have witnessed the hasty manner in which he is removed, and the division of his estate, when his face is lost, his memory forgotten, and his doorway forsaken, as if he had not mixed with those who keep their word, nor inhabited the lands.
Therefore, beware the horror of a day on which not so much as the weight of an ant on the scale will be despised."
According to 'Abd al Rahmaan bin Mahdee - Sufyaan: 'Umar bin 'Abd al 'Azeez said:
"He who acts without knowledge causes more corruption than good, and he who does not consider his speech to be part of his actions sins repeatedly. Satisfaction is scarce, and the true believer should rely on sabr (patience).
Allah Ta'aala never bestowed a blessing upon one of His servants and then took it away from him, giving him sabr in return for that which was taken away, except that the replacement was better than what was taken away from him."
Then he recited the following verse:
"Surely the patient will be paid their wages in full without reckoning."[Qur'an 39:10]
Source