While a valid point, small nerd correction here: the time when Vivec tells Nerevar to reach heaven by violence and he goes to the moons is not the first nor the most important time it comes up. It is absolutely not a throwaway term.
The first time the line is introduced in Sermon 6:
You have discovered the sixth Sermon of Vivec, which was hidden in the words that came next to the Hortator.
[...]
Six are the formulas to heaven by violence, one that you have learned by studying these words.
Herein "heaven by violence" refers to just any form of ascension to godhood whatsoever, since all walking ways require engaging in the violence of the universe - the Tri-Angular Truth, the original betrayal from which the Aurbis sprung forth - and reenacting it yourself. Different paths to reenactment became codified as the walking ways, hence, "formulas to heaven by violence".
The second time it comes up in Sermon 15, the one where Vivec introduces Nerevar to the concept of the Sharmat:
'You alone, though you come again and again, can unmake him. Whether I allow it is within my wisdom. Go unarmed into his den with these words of power: AE GHARTOK PADHOME [CHIM] AE ALTADOON. Or do not. The temporal myth is man. Reach heaven by violence. This magic I give to you: the world you will rule is only an intermittent hope and you must be the letter written in uncertainty.'
Here he is directly instructing Nerevar to ascend and become the Sharmat's equal, which necessitates that Nerevar must first overcome Vivec himself (earlier in the same Sermon, "The ruling king will remove me, his maker. This is the way of all children."). Vivec will be the one to judge whether he is worthy and capable of the station (Sermon 13: "If there is to be an end I must be removed. The ruling king must know this, and I will test him. I will murder him time and again until he knows this.")
Then in Sermon 16, the line comes again:
Nerevar said, 'I am afraid to become slipshod in my thinking.'
Vivec said, 'Reach heaven by violence then.'
Nerevar doubts his abilities and so Vivec advises him to complete his journey to apotheosis, which will leave no room in him for doubt. That is why he goes to raid the Parliament of Craters, who directly call him out for his flaws and belittle his supposed "royalty", as they are not "the earth under his temporal domain" and thus do not recognize his authority. After his failure to subdue them, Vivec finds him in Sermon 17 and takes him around the world, showing him the Red Mountain where he will inevitably face the Sharmat.
Sermon 18, then is the last one to mention the line:
This sermon is forbidden.
In this world and others EIGHTEEN less one (the victor) is the magical disk, hurled to reach heaven by violence.
This sermon is untrue.
The ending of the world is ALMSIVI.
The Hurling Disk is an existing symbolic image in TES which represents Nirn itself, the Wheel with no center, hurling through the void to reach an invisible heaven. Sermon 18 in particular tackles Vivec's own doubts about his divinity and whether the Tribunal are truly an improvement over the Three Good Daedra they mantled, while he muses on the way their apotheosis revised the universe.
For this reason I'd also call attention to the final line: unlike in the other Sermons, where they end with "The ending of the words is ALMSIVI", this one says "The ending of the world is ALMSIVI". By ascending, the ALMSIVI have destroyed the previous world where they did not yet exist as gods, and time had been rewritten. Sermon 17 alludes to it even more subtly - Vivec and Nerevar engage in combat and Nerevar is wounded, "marked for all to see", but then he heals the wound. In this revised timeline, Nerevar did not die by their hand.
All of these musings are fundamentally talking about the nature of godhood and its effect - its violence - upon the world. One must engage in violence to escape it, and to continue exercising one's power is inflicting that violence upon the world. You don't even realize you do it.
Subsequent are the revisions, differentiated between hope and the distraught, situations that are only required by the periodic death of the immutable. Cosmic time is repeated: I wrote of this in an earlier life. An imitation of submersion is love's premonition, its folly into the underworld, by which I mean the day you will read about outside of yourself in an age of gold. For on that day, which is a shadow of the sacrificial concept, all history is obliged to see me for what you are: in love with evil.
