Ruling on giving a special gift to the dutiful child as a reward for his dutifulness

Q: Some people have one child who distinguishes himself from his siblings in his dutifulness and affection toward his parents. His father gives him special kindness and gifts because of this distinguished dutifulness. Is it just to give the child who is distinguished by his dutifulness a reward for his dutifulness?

A: There is no doubt that some children are better than others; this is a known fact. However, the father must not prefer one over the others because of this. Rather, he must be just, based on the saying of the Prophet (peace and blessings be upon him): Therefore, it is not permissible for him to prefer one because he is better or more dutiful than the other. Rather, he must be just among them and advise them all so that they may be upright in their dutifulness and in obedience to Allah and His Messenger. However, he must not prefer some of them over others in gifts, nor make a bequest for some of them without the others. Rather, they are all equal in inheritance and gifts according to what the Shari'ah has prescribed regarding inheritance and gifts. He must be just among them as stated in the Shari'ah, where the male receives the share of two females. So if he gives one of his sons a thousand, he gives the daughter five hundred. If they are guided and they are lenient, and they say, "Give our brother so much," and they show clear leniency, then there is no harm. If they say, "We allow you to give him a car or give him so much," and it is clear to him that their leniency is genuine, not just out of politeness or fear of him, then there is no harm.
The point is that he must seek justice, unless the children are guided and equal, whether they are males or females, and they allow one of them to be given something for specific reasons, then there is no harm, for the right belongs to them.