Hell is nowhere other than in the Mind

Krishna now proceeds to summarize the whole enunciation of the 16th chapter:

"Passion, hatred and greed are the three-fold door to hell in this world. Therefore, these three are to be renounced."  (Bhagavadgeeta 16.21)

Three are the doors, Krishna says, leading one to hell. These are nowhere other than in the mind of every one. When passion, hate or greed emerges in the mind, instantly opens up the direct door to hell too. Where is hell in one's own life then? It abides in the mind itself. These doors can be safely shut. That will verily bring the victory over hell. Krishna's statement is not new. He has been emphasizing it throughout.
In the second chapter, when analyzing the status and value of Vedas, particularly their ritualistic pronouncements, Krishna clearly stated how even the Vedic votary falls a victim to kaama, bhoga and aishvarya, thereby abandoning all his discretion and discrimination (2.42-44).
In describing the sthitaprajna and sthitadhee also, he specifically pointed out how sanga (attachment) to an object grows into strong desire and greed, which then leads, step by step, to anger, hate, delusion and downfall (2.62,63). The same emphasis was again made in the 3rd chapter (3.34). In another way, he pointed out the same truth in the 5th chapter (5.23) too.
The warning against kaama and krodha continues throughout the discussion. Here too he refers to the same plight by describing the inner doors to hell. The main thread of the discussion thus becomes quite evident, emphatic and supreme. Krishna concludes in verse 16.22.

"True spiritual evolution consists in gaining freedom from this threefold hell. Once he ensures this, the seeker is safe and will head towards supreme redemption."

Krishna emphasizes that all the Scriptures are there to help humanity to tread this great path of inner purity and redemption. If any one were to disregard the benevolent voice of the Scriptures, that would be to bring about degeneration and downfall to himself as well as the society (16.23).
Harih Om Tat Sat. Jai Guru.