One night, Caliph Umar (radiAllahu anhu) as usual went in disguise with his companion Ibn Abbas to see the condition of the people. They strolled from one quarter to another. At last they came to a colony where poor people lived.
While passing by a small house, the Caliph (radiAllahu anhu) heard a whispering talk within. The mother was telling her daughter that the amount of milk fetched by her for sale that day was very little. She told her that when she was young, and used to sell milk, she always mixed water with milk, and that led to considerable profit. She advised her daughter to do the same.
The girl said, "You adulterated milk, when you were not a Muslim. Now that we are Muslims, we cannot adulterate milk." The mother said that Islam did not stand in the way of adulteration of milk.
The daughter said, "Have you forgotten the Caliph's order? He wants that the milk should not be adulterated." The mother said, "But the Caliph has forgotten us. We are so poor, what else should we do but adulterate milk in order win bread?"
The daughter said "Such a bread would not be lawful, and as a Muslim I would not do anything which is against the orders of the Caliph (radiAllahu anhu) , and whereby other Muslims are deceived."
The mother said, "But there is neither the Caliph nor any of his officers here to see what we do. Daughter you are still a child. Go to bed now and tomorrow I will myself mix the milk with water for you."
The girl refused to fall in with the plan of her mother. She said, "Caliph may or may not be here, but his order must be obeyed. My conscience is my Caliph. You may escape the notice of the Caliph and his officers, but how can we escape the notice of Allah and our own conscience." Thereupon the mother remained quiet. The lamp was extinguished and the mother and the daughter went to sleep.
The next day, Caliph Umar (radiAllahu anhu) sent a man to purchase milk from the girl. The milk was unadulterated. The girl kept her resolve.
Caliph Umar (radiAllahu anhu) turned to his companion and said, "The girl has kept her resolve in spite of the exhortation of her mother. She deserves a reward. What reward should I give her? She should be paid some money," said Ibn Abbas.
Caliph Umar (radiAllahu anhu) said, "Such a girl would become a great mother. Her integrity is not to be weighed with few coins; it is to be measured in the scale of national values. I shall offer her the highest award in my gift, and which shall also be in the highest interest of the nation."
The Caliph (radiAllahu anhu) summoned the daughter and the mother to his court. The mother trembled as she stood before the mighty ruler. But the girl faced the Caliph boldly and with great equanimity.
She was beautiful, and there was an impressive dignity about her. Then before the gathering, Caliph Umar (radiAllahu anhu) related how he had overheard the mother and the daughter, and how in spite of the exhortations of the mother the daughter had kept her resolve.
Someone suggested that the mother should be taken to task. The Caliph (radiAllahu anhu) said that ordinarily he would have punished the mother, but he had forgiven her for the sake of her daughter.
Turning to the girl the great Caliph (radiAllahu anhu) said, "Islam needs daughters like you and as a Caliph of Islam it devolves on me to reward you by owning you as a daughter."
The Caliph called his sons, and addressing them said, "Here is a gem of a girl who would make a great mother. I desire that one of you should take this girl as wife. I know of no better bride than this girl of sterling character. In matters of wedlock, it should be the character and not the stature in life that should count."
Abdullah and Abdur Rahman the elder sons of the Caliph (radiAllahu anhu) were already married. Asim the third son was yet unmarried, and he offered to marry the girl. Thereupon with the consent of the milkmaid and her mother Asim was married to the girl, and milkmaid became the daughter-in-law of the Caliph(radiAllahu anhu) .
From this union was born a daughter Umm Asim, who became in due course the mother of Umar bin Abdul Aziz. Umar bin AbdulAziz was elected as Caliph and served for a short period during 717 - 720.
While other Caliphs of the Ummayad dynasty reveled in luxury, Umar bin Abdul Aziz as a Caliph set up standards for austerity and simplicity following in the footsteps of Caliph Umar (radiAllahu anhu) , the second Caliph of Islam.
It is said that if ever there was a noble Caliph after the first four Rightly guided Caliphs, such a man was Umar bin Abdul Aziz. And he inherited the noble qualities of the milkmaid who married the Caliph's son, and those of Caliph Umar Farooq who had the eye to discern the nobler qualities of sterling character in a poor girl.