Praise be to Allah.
Firstly: Is the father obliged to spend on his children’s education?
The father is obliged to spend on his children until they grow up and become able to earn a living. That includes spending on education. According to some of the fuqaha’ – namely the Hanbalis – he is obliged to spend on his son until his son grows up and is able to earn a living, so long as the son is not actually working and does not have any money that he can spend on himself.
It says in al-Insaaf (9/289): His words: “his sons [and grandsons] no matter how far the line of descent reaches” include strong, healthy, adult children, if they are poor. And this is correct. End quote.
See: al-Mughni (9/258).
Abu Haneefah said: He [the father] should spend on his son until he becomes an adult. If he becomes an adult and is healthy, then the obligation of spending on him ceases, but the obligation to spend on a daughter does not end until she gets married.
Maalik said something similar, but he said that women should be spent on until they get married and their husbands consummate the marriage with them.
According to the Shaafa‘is, it is obligatory to spend on the maintenance of an adult child only in the case of his being incapacitated due to chronic disability or sickness. If he is healthy, there is no obligation to spend on him.
Therefore, according to the view of the majority of fuqaha’, the father is not obliged to spend on his son’s university education, because at that time the son is an adult.
According to the Hanbali madhhab, the father is obliged to spend on his son so long as the latter is poor, whether he is sick or healthy, so long as he cannot find work.
Secondly: Is the son obliged to give his salary to his father?
If the son is working and earning money, he is not obliged to give it to his parents, unless they are in need of maintenance, in which case he is obliged to spend on them according to their need; he is not obliged to hand over everything that he earns.
Ibn Qudaamah (may Allah have mercy on him) said: It is obligatory for a man to spend on his parents and on his children, both male and female, if they are poor and he has the means to spend on them.
With regard to scholarly consensus, the scholars are unanimously agreed that spending on poor parents who have no income or wealth is an obligation on the wealth of their son. All of the scholars from whom we acquired knowledge are unanimously agreed that a man is obliged to spend on his minor children who have no wealth. End quote from al-Mughni (8/211).
But the father may take something from his children’s wealth, if he needs to, on condition that that is not detrimental to them, and that he does not take from one of them in order to give to another.
The basic principle regarding that is the hadith narrated from ‘Amr ibn Shu‘ayb, from his father, from his grandfather, according to which a man came to the Prophet (blessings and peace of Allah be upon him) and said: O Messenger of Allah, I have wealth and children, and my father wants to take all my wealth. He said: “You and your wealth belong to your father. The best of what you eat is that which is from your earnings and the wealth of your children in part of your earnings. So eat from it and enjoy it.”
Narrated by Ahmad (6678), Abu Dawood (3530), Ibn Maajah (2292). This report has some isnaads and corroborating evidence which render it saheeh. See: Fath al-Baari (5/211) and Nasab ar-Raayah (3/337).
Based on that, if your parents are not poor and in need of maintenance, then you are not obliged to give them anything of your wealth.
But if one of them is in need of money, it is permissible for them to take from you, subject to the two conditions mentioned above.
It is not obligatory to follow a tradition which imposes something that is not enjoined in Islamic teachings.
What we advise you to do is to treat your parents kindly, honour them and give them something of your wealth that will not be detrimental to yourself. It is permissible for you to keep from them how much you earn, and to use double entendres, such as saying that you earn one thousand, for example, when in fact you earn two thousand, because you are not lying when you say that you are earning one thousand.
We ask Allah to rectify your affairs and guide you.
And Allah knows best.