Threat of parents favoritism to children
Prophet Muhammad SAW even rebuked parents who are known to be favoritism towards their children. As narrated in a hadith..
From Nu'man bin Basyir ra that his father came to take him to the Messenger of Allah, he said, "Indeed I have given a gift in the form of a slave of mine to my son." Then the Messenger of Allah said, "Do all your children receive gifts like your son?" FatherAn-Nu'man replied, no. Then the Messenger of Allah asked, "Would you be happy if they (your children) all serve you equally?" Then An-Nu'man's father replied, "I will, O Messenger of Allah." Then the Messenger of Allah said: "Then don't do it (favouritism)." (HR. Muslim)
While in another Muslim narration which was also narrated by Bukhari, with the addition of the sentence
The Prophet said: "Fear Allah and be fair among your children." Then he returned and took back his gift.
In this hadith, we can see that the Messenger of Allah forbade his people to behave favoritism towards their children, because if parents want all their children to be filial, then he must behave fairly or equally to each child.