Continuing the discussion of how various despicable acts may not be technically punishable, sometimes the rabbis allowed for extra measures to rein in wholesale abuse and disregard for the law or social order. Therefore, even though one who repeatedly violates a prohibition in the Torah is technically not subject to capital punishment, the Mishna on amud beis rules:
One who was flogged for violating a prohibition and then repeated the violation and was flogged again assumes the status of a forewarned transgressor. The court places him into the vaulted chamber [lakippa] and feeds him barley bread until his belly ruptures due to the low-quality food, and he dies.
Rashi adds an explanatory note regarding his behavior: “Since he committed the sin repeatedly and was flogged, he abandoned himself to sin.”
The Rav (Reshimos Shiurim) explains that it is not necessarily the number of times per se, rather if one evidences such an attitude, he is now liable for death.
I presume the Rav means that such a person is a threat to basic moral order, and therefore, he must be stopped.
This punishment was quite gruesome. The Gemara explains in more detail:
First, the court gives him sparing bread and scant water until his intestines contract due to his starvation diet. Then, the court feeds him barley bread that expands in his innards until his belly ruptures.
I believe that within this gruesome punishment there is a metaphoric message. It is notable that first he is starved and then he is overfed, leading to his suffering and death. The sages are hinting at the nature of sin. It is human to sin, and sometimes our desires can get the better of us. As Koheles (7:20) states: “For there is not one good man on earth who does only good and does not sin.” That is regrettable, but does not necessarily incur God’s wrath. However, if one’s attitude is to behave as if all is permitted with no remorse, then his sins are much less forgivable. He starts out being starved, as if to say, “OK, we get it, you had lust.” But then he dies by being engorged with food, which is to say, “We don’t hold your lust or weakness against you, but did you have to be a chazer? Now, that is unforgivable!”
Translations Courtesy of Sefaria, except when, sometimes, I disagree with the translation 
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Rabbi Simcha Feuerman, Rabbi Simcha Feuerman, LCSW-R, DHL is a psychotherapist who works with high conflict couples and families as well male sexual health. He can be reached via email at simchafeuerman@gmail.com