Assalaam alaykum. Why is it that even after raising children on the way of Prophet Muhammad, sallallaahu ʻalayhi wa sallam, the children sometimes do not follow their religion properly or go astray? It is said that if we are good to our parents, then our children will be good to us, does this happens for every individual? I have seen people who were good to their parents, but their own children are undutiful towards them?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ʻalayhi wa sallam, is His slave and Messenger. 

There is no doubt that parents are enjoined to raise their children according to the standards of righteousness and goodness in the hope that they will grow up to be righteous and pious Muslims who walk the path of goodness, piety and righteousness, as enjoined in the verse that reads (what means): {O you who have believed, protect yourselves and your families from a Hellfire whose fuel is people and stones, over which are (appointed) angels, harsh and severe; they do not disobey Allaah in what He commands them but do what they are commanded.} [Quran 66:6]

Parents are only required to employ the available means to guide their children to the path of righteousness and goodness; their task is merely confined to leading and instructing them to the straight path, urging them to abide by it, which is also the task of the Prophets of Allaah and reformers. Allaah, The Exalted, says (what means): {And thus We have revealed to you an inspiration of Our command. You did not know what is the Book or (what is) faith, but We have made it a light by which We guide whom We will of Our servants. And indeed (O Muhammad) you guide to a straight path.} [Quran 42:52]

As for the divinely-given guidance, that is when one is enabled by Allaah to follow guidance, causing the light of faith to penetrate into the heart. No one can play any role or has any interference in this type of guidance but Allaah. He says (what means): {Indeed (O Muhammad) you do not guide whom you like, but Allaah guides whom He wills. And He is most knowing of the (rightly) guided.} [Quran 28:56]

For more benefit, please refer to fatwa 8976.

There is no doubt that there is divine wisdom behind the misguidance of the children of devout parents; verily, Allaah, The Exalted, knows all what is preserved in the hearts and knows who is worthy of such grace because of the purity of the receiver and who is unworthy of it given his corruption. Ibn Al-Qayyim wrote:

"Allaah guides him who wants to be guided, which is a great blessing. On the other hand, He sends astray those who are unworthy as well as those who are unwilling to receive the blessings of Allaah, so He deprives them of His blessing but not His justice. Such people are divided into two kinds. The first kind is him whom Allaah leaves to stray due to his misguidance as he turned away from Allaah, preferring His enemy and neglecting to remember and thank Him. As a result, he deserves to be abandoned by Allaah. The second kind is those whom Allaah is unwilling to support at all because He knows that they do not value the guidance of Allaah. Such people are not thankful to Allaah and do not praise Him, and this is the reason for their being deprived of His blessings. Allaah, The Exalted, says (what means): {And thus We have tried some of them through others that the disbelievers might say, 'Is it these whom Allaah has favored among us?' Is not Allaah most knowing of those who are grateful?} [Quran 6:53] - {Had Allaah known any good in them, He would have made them hear. And if He had made them hear, they would (still) have turned away, while they were refusing.} [Quran 8:23]"

If the father employed all the available means and strove in providing a righteous and good upbringing for his son, but he went astray anyway, then he should not be distressed about that; Prophet Nooh (Noah) was a wise and knowledgeable Prophet of Allaah; nevertheless, his son went astray. Allaah, The Exalted, says (what means): {He said, "O Nooh, indeed he is not of your family; indeed, he is (one whose) work was other than righteous, so ask Me not for that about which you have no knowledge. Indeed, I advise you, lest you be among the ignorant."} [Quran 11:46]

For more benefit, please refer to fatwa 85041. This is as far as the first part of the question is concerned.

As for the second part of the question, the Prophet, sallallaahu ʻalayhi wa sallam, said, "Be dutiful towards your parents and your children will be dutiful towards you." [Al-Haakim in Al-Mustadrak] Several Hadeeth scholars declared its chain of narration weak, and Al-Albaani cited it (as weak) in his book As-Silsilah Adh-Dhaʻeefah.

Assuming that this hadeeth had been authentic, it would have agreed with the principle, "You reap what you sow." This is of course the common scenario; however, a given deed might not be rewarded  with a reward of its same nature in some cases because of the lack of one factor from the equation or the presence of a given impediment.

Moreover, the corruption of parents incurs the corruption of children; however, the influence of the parents' corruption might change for a wisdom only known to Allaah, like in the case of Prophet Ibraaheem (Abraham) ; his father was a disbeliever, and he was the Imaam of the monotheists. Divine wisdom may entail that parents and children be afflicted with such undutifulness. The son may be afflicted for the corruption of his intention, evil inner self, and sins; Allaah, The Exalted, says (what means): {And We will surely test you until We make evident those who strive among you (for the cause of Allaah) and the patient, and We will test your affairs.} [Quran 11:37] And the parent may be tried with the undutifulness of his child so that Allaah would test his patience and raise his rank. Abu Hurayrah narrated that the Prophet, sallallaahu ʻalayhi wa sallam, said, "Trials will continue to befall the believing man and woman with regard to themselves, their offspring, and their wealth until they meet Allaah with no sin on them." [At-Tirmithi]

Allaah knows best.