What is the authenticity of the hadith: "Whoever harms, Allah will harm him; and whoever causes hardship, Allah will cause hardship for him," and why do we see people harming and causing hardship to others, yet Allah does not cause hardship for them?

The meaning of the Hadith: "Whoever harms [others], Allah will harm him; and whoever causes hardship [to others], Allah will cause hardship to him," is sound, for it is a retribution of the same kind as the deed. This is established in both Islamic law and divine decree. And what is observed of the oppressor's prosperity in this world does not contradict the Hadith for several reasons:

1. The oppressor may suffer from internal psychological distress and misery, which puts him in a state of discomfort despite outward appearances of luxury. 2. Punishment for the oppressor may be delayed as a trial and test for people. This delay might also be a gradual enticement [istidrāj] for him to increase in his transgression, so that when the punishment eventually comes, it is more severe and painful. 3. The Hadith does not specify that the punishment must occur in this world. The harm and hardship may be in the Hereafter, and the torment of the Hereafter is more severe and lasting. The hastening of punishment in this world may be a sign that Allah wills good for His servant.