Praise be to Allah.
Children are one of the blessings of this worldly life, as Allah says (interpretation of the meaning):
“Wealth and children are the adornment of the life of this world” [al-Kahf 18:46]
They are the apple of their parent’s eye and the joy of their hearts, so how can they pray against them?
The Prophet (peace and blessings of Allah be upon him) forbade praying against one’s children, one’s wealth and one’s own self, lest that be at a time when du`as are answered. He (peace and blessings of Allah be upon him) said: “Do not pray against yourselves, do not pray against your children, do not pray against your wealth, lest that coincides with a time when Allah is asked and He gives, so He answers your prayer.” Narrated by Muslim (3014).
The parent’s du`a’ for or against his child is answered. The Prophet (peace and blessings of Allah be upon him) said: “Three prayers are undoubtedly answered: the prayer of one who is wronged, the prayer of the traveller and the prayer of a father for his child.” Narrated by Ibn Maajah (3862); classed as saheeh (authentic) by al-Albaani in Silsilat al-Ahadith al-Saheehah (596). The version narrated by Imam Ahmad says: “the prayer of a father against his child.”
A mistake that is made by many fathers and mothers is that they pray against their children if the latter do something that makes them angry. What they should do is pray for them to be guided and for Allah to set their affairs straight.
By His mercy, Allah does not answer the du`a of parents against their children if it is at a time of anger, because Allah says (interpretation of the meaning):
“And were Allah to hasten for mankind the evil (they invoke for themselves and for their children, while in a state of anger) as He hastens for them the good (they invoke) then they would have been ruined. So We leave those who expect not their Meeting with Us, in their trespasses, wandering blindly in distraction” [Yoonus 10:11]
Ibn Katheer (may Allah have mercy on him) said in his Tafseer (Exegesis) (2/554):
Here Allah tells us of His forbearance and kindness towards His slaves, for He does not answer them when they pray against themselves or their wealth or their children at moments of anger. He knows that they do not really mean any ill, so He does not answer them out of kindness and mercy, as He does when they pray for themselves or their wealth or their children for goodness, blessing and growth. End quote.
And Allah knows best.