Bhagavad Gita Verse 19, Chapter 16

taanaham dvishataha krooraansamsaareshu naraadhamaan |
kshipaamyajastramashubhaanaasureeshveva yonishu || 19 ||
 
Those who are hateful, cruel, they are wretched in this world. Definitely, I cast such inauspicious people into devilish wombs, repeatedly.
 
taan : those
aham : aham
dvishataha : hateful people
krooraan : cruel people
samsaareshu : in this world
naraadhamaan : wretched people
kshipaami : I cast
ajastram : repeatedly
ashubhaan : inauspicious people
aasureeshu : devilish
eva : definitely
yonishu : wombs
 
What happens to people who, through their devilish behaviour, cause trouble to everyone and everything around them? Shri Krishna says that through their behaviour, such people become naraadhamaan, the lowest of the humans, the most wretched category of people in this world. They mistakenly think that they are above the law. But they are not above the law of karma. Ishvara ensures that such people get the punishment that they deserve, which is rebirth into devilish wombs such as those of animals and insects.
 
Let us first examine the symbolic meaning of this shloka. As we have seen in earlier chapters, we are at our best when the intellect has supremacy over our senses and our mind. But in people with devilish attributes, this picture becomes topsy turvy. The senses rule over the intellect. Logic, reason, duty, all such characteristics of the intellect are suppressed. Only sensual consumption takes precedence.
 
Now lets look at the shloka. Each time someone gives precedence to their senses as opposed to their intellect, their ego, their sense of I, ties yet another know, makes yet another association with the senses. Symbolically, each time this happens, they take birth in a devilish womb. This situation cannot carry on for a while. History is full of tyrants and dictators who let their greed get the better of them, made one miscalculation, and died horrible deaths at the hands of their subjects or their enemies.
 
Literally, this shloka asserts the working of the law of karma. Out of nowhere, we find that we experience unexpected professional success, monetary and personal gains. Similarly, we find that unexpectedly, we have to go through a rough, painful patch. Good or bad actions that we have performed in our present life, or perhaps in a previous life, always bring their consequences back to us. In fact, whenever we are going through a rough patch, we should be glad that the consequences of our bad actions are getting exhausted.
 
Similarly, people who commit devilish actions also get their payback. But their payback is harsher than what most of us go through. Shri Krishna says that such people take birth into species such as animals and insects. In such species, there is no scope for using the intellect to gain self realization and liberation. Only humans have this ability. Any state where we cannot access the intellect, whether we are in a human form or not, is the worst punishment possible.