God does not punish a person directly, for He is the source of only good and loving-kindness. However, when a person sins, he thereby creates a barrier between himself and the divine goodness coming from above. This leaves him vulnerable to misfortune and calamity. According to this understanding, punishment is a natural result of man’s own actions.

Man is treated in accordance with his actions:

The general principle in all matters is that “a person is measured according to the measure that he measures” (Mishna Sota 1:7). The explanation of this principle is not known by many, for they attempt to explain this matter with regard to God, blessed be He, in a manner similar to the way people repay [others for their deeds]; each one repays his friend according to the good or bad that he did to him. But this is not the case with regard to God, blessed be He, God forbid. For with God, blessed be He, there is nothing other than everlasting goodness, loving-kindness, and mercy…. What [the Sages] of blessed memory meant when they said with regard to Him, blessed be He that “a person is measured according to the measure that he measures,” is that a person will be repaid in accordance with his actions, whether good or not. For exactly corresponding to the manner of a person’s thoughts and actions will he draw upon himself blessing or the opposite…. But it is man himself who causes himself to be liable [for misfortune] when he strays from the upright [path], and he [thereby] removes from himself the prerequisites that dispose him to receive goodness.

All misfortune that happens to a person comes about because the Divine Presence is hidden:

This is analogous to one who walks on a path that is straight and free of stones or other impediments, but is bordered on both sides by a thorny fence. If one passed by and scraped against the fence and was injured, it cannot be truthfully said about this person that God wanted him to be injured, but rather that he was the cause [of his own injury] because he was not careful to walk straight. Similarly with regard to a sinner, the attribute of strict judgment holds him accountable for his sin no matter what, but it cannot be said that the good God wants him to be held accountable. Rather, when goodness is withheld from him due to his sin, harm will find him. [The Sages] of blessed memory said similarly: “No evil comes from above” (Bereshit Rabba 51:3). The principle we are expressing is that any negative occurrence that comes upon a person occurs because the face of God is hidden from the person. (Sefer HaĤinnukh, Mitzva 171)

Blessing and punishment are the natural results of the performance of mitzvot or sins, not externally imposed punishments. A good act brings about a flow of divine goodness in the upper spheres to the source of Jewish souls, resulting in blessing in the lower world. Conversely, sin blocks the channel through which divine goodness flows, and the results are felt in this world as misfortune.

Reward and punishment are a natural result of man’s actions:

Know that the blessings and curses written in the Torah are not merely reward or punishment. Rather, they are truly natural [results of man’s actions], like the fact that one who sows will reap, as the verse states: “He who works his land will have bread to satisfaction” (Proverbs 12:11). In the opposite [case of one who sins, the result is] the opposite…. This is the concept that all of the Torah’s blessings are natural.

Sin affects the channels of the divine flow of influence:

When people sin, the channels of grace decrease and those of strict judgment increase. The entire world then experiences pain and lack. The worst of all is when the highest channels are completely blocked, and evil forces and foul waters are drawn from outer channels. Then there is destruction of countries, upheaval, and harrowing exiles. The admonitions written in the Torah refer to this state of affairs. In summary, in accordance with [the divine abundance] drawn by the community of Israel above, so is the fate of the Jewish people below, so that different events causing death or life come about corresponding to the power that is drawn from upper levels. (Rav Menaĥem Recanati, Commentary on the Torah, Beĥukotai)

Further reading: For more on the concept of “no evil comes down from above,” see A Concise Guide to the Sages, p. 229.