Sometimes G-d sends good to the wicked for the following reasons:
1. A previous good deed he did, to pay him in this world, as written "And He repays those He hates to their face, to destroy them" (Deuteronomy 7:10) which the Targums render: "He pays those He hates for their good deeds during their lives to destroy them".
2. As a temporary deposit, until G-d gives him a righteous son who is worthy of it, as written "he prepares but the tzadik will wear it" (Job 27:17), and "to the sinner He has given a preoccupation to gather and to accumulate, to give to him who is good in G-d's sight" (Ecclesiastes 2:26).
3. Sometimes the money is the chief cause of his evil (in the next world) or death (in this world), as written "There is a grievous evil that I saw under the sun; riches kept by their owner for his harm." (Ecclesiastes 5:12)
4. Sometimes it is to give him time to repent and become worthy of it, as you know of the story of Menashe.
5. His father did good and it is fitting to benefit him in the merit of his father, as said to Yehu ben Nimshi "four generations of your descendants will sit on the throne of Israel" (2 Kings 10:30), and "He who walks innocently is righteous; fortunate are his sons after him." (Proverbs 20:7), and "I was young, and have aged, and I have not seen a righteous man forsaken nor his descendants begging bread." (Psalm 37:25).
6. Sometimes it is to test those who are deceptive or have an evil interior. When they see the wicked prosper, they quickly stray from the service of G-d and hasten to win the favor of the wicked and to learn from their actions. In this way it will be clarified the pure men to G-d and it will be demonstrated who was faithful to G-d in bearing at a time when the wicked rule and persecute him. He will receive reward from the Creator for this, as you know of the story of Eliyahu and Isabel or Yirmiyahu and the kings of his generation.
If one asks: Behold we see some tzadikim (very righteous people) which do not receive their livelihood except after hard and strenuous toil, while many transgressors are at ease, living a good, pleasant life?
We will say: The prophets and the chasidim (extremely pious) already investigated this matter. One of them said "(Righteous are you, O L-rd, when I plead with You: yet let me talk with You of your judgments:) Why does the way of the wicked prosper? why are all they happy that deal very treacherously?" (Jeremiah 12:1), and another "Why do You show me iniquity and look upon mischief; and plunder and violence are before me; and the one who bears quarrel and strife endures." (Habakkuk 1:3), and "for a wicked man surrounds the righteous; therefore, justice emerges perverted." (Habakkuk 1:4), and "Why should You be silent when a wicked man swallows up one more righteous than he?" (Habakkuk 1:13), and another one said "Behold these are wicked, yet they are tranquil in the world and have increased wealth." (Psalm 73:12), and "But for naught I cleansed my heart and bathed my hands with cleanliness" (Psalm 73:13), and another said "And now we praise the bold transgressors, those who work wickedness are built up, they tempt G-d, and they have, nevertheless, escaped." (Malachi 3:15), and many more like this.
Moshe Rabeinu commented on this in the torah saying (Deuteronomy 29:28) "the hidden things belong to G-d"..and the wise man said in connection to this "If you see the oppression of the poor, and perverting of justice and righteousness in a province, marvel not at the matter" (Ecclesiastes 5:7), and the verse says: "the Rock, His deeds are perfect for all His ways are justice" (Devarim 32:4).
Reasons why we suffer according to R Bachya
1. A previous sin for which it is necessary to pay him for it, as written "the tzadik will pay in the land" (Mishlei 11:31)
2. In the way of exchanging, to pay him more good in Olam Haba (the afterlife), as written "to benefit you in your end" (Deuteronomy 8:16)
3. To demonstrate his good bearing and good acceptance of suffering in the service of G-d, so that others will learn from him, as you know from the matter of Job.
That he receives everything with a good countenance, and he does not rebel in sufferings so that others will learn from him and see him and notice him and desire to serve G-d even though they don't have all their lusts, and even though they are in poverty, hardship or in painful sicknesses as we find with Iyov (Job) and many other sages, who were in suffering yet did not stop from torah and service, and as is known of Hillel who was extremely poor, and others who needed to labor for their livelihoods and nevertheless studied the torah.
Also, to show the world that the Tzadik bears the bad of this world, with good patience and a good countenance, and despite his suffering, he does not budge away from the service of his Creator in order to ease the bad. Unlike the wicked, that even for something he is forced to bear, he bears it with an angry heart, and therefore he throws off the yoke of service in order to ease his troubles.
He bears his sufferings and is not begrudging towards G-d and accepts them with a good countenance)
Due to the wickedness of his generation, G-d tests him with poverty, hardship, or sickness to demonstrate/contrast his piety and service of G-d unlike them, as written "Indeed, he bore our illnesses, and our pains he carried them" (Isaiah 53:4). won't learn from him and they will get no benefit from this. Nevertheless, G-d tests him in order to demonstrate his level and worth and contrast it with them. That even though they are in enjoyment and he is in a life of suffering, they are ungrateful towards G-d while he is good with Him and serves Him in truth and wholeheartedly. The intent in this is so that they will acknowledge G-d's justice in the end of days when they will see the exceedingly great reward of the Tzadik. And like our sages said in Pirkei Avot 5:3, "Avraham was tested with ten trials..to show his high esteem."
Due to the wickedness of the generation, sometimes G-d sends suffering to a Tzadik to atone for the sins of the generation (to avert disasters or the like), and without a doubt, his reward will not be withheld and the wicked will be paid what they deserve, as Rashi explained on the verse he cited)
5. Due to his not being sufficiently zealous in standing up for G-d, and exacting justice from men of his generation, as you know from the story of Eli and his sons, as the verse says "And it will be that everyone who is left in your house, will come to prostrate himself before him for a silver piece and a morsel of bread" (Samuel 2:36). As the talmud says (Shabbat 54b):
"Whoever can forbid his household [to commit a sin] but does not, is seized (held accountable) for [the sins of] his household; [if he can forbid] the men of his city, he is seized for [the sins of] the men of his city; if the whole world, he is seized for [the sins of] the whole world")
There is another general purpose to suffering for everyone including children as explained in Bachya’s Duties of the Heart. Here is an excerpt:
Later on he is subjected to illnesses and meets with painful incidents so that he recognizes the world, and that its nature is not concealed from him. Thus he is put on his guard against trusting in this world thereby permitting his lusts to rule over him, in which case he would become like the animals that neither think nor understand; as it is written "Be ye not as the horse or as the mule which have no understanding" (Psalm 32:9).
"illnesses" - such as chicken pox and measles. "painful incidents" - many weaknesses come in the boyhood years.
"Be ye not as the horse or as the mule" - they need to be leashed and muzzled, so too man. The painful incidents humble his lusts. "so that he recognizes the world" - how a person's situation can change swiftly from contentment to pain so that he realizes not to trust in it and its tranquility - rather to always be afraid and to seek refuge in G-d's shadow.
If a human being had only constant good in this world, he would forget and not recall the matters of his final end, and he would trust (hope) in this world and follow the musings of his heart and his lusts for all of his days. Therefore, it was among the divine plan to send him sometimes bad illnesses, even during his youth in order that he recognize and know that there is no complete good in this world. And even if he is currently in a very good situation, the bad illnesses can come and ruin his joy, so that he won't trust in this world.
Another reason for suffering explained by the kabbalists is to rectify something done in the past. So for example, someone born into a life of misery and suffering for no apparent reason whatsoever - this may be in order to rectify something from previous generations.
Theological Insights from Rabbi Eved Banah the North American Rebbe of Ani Judaism