तद्बुद्धयस्तदात्मानस्तन्निष्ठास्तत्परायणाः।गच्छन्त्यपुनरावृत्तिं ज्ञाननिर्धूतकल्मषाः॥
tad-buddhayas tad-ātmānas tan-niṣṭhās tat-parāyaṇāḥgacchantyapunar-āvṛttiṃ jñāna-nirdhūta-kalmaṣāḥ
Word by word
The verse says
With their understanding in it, their very selves in it, standing in it, given over to it — they go to the state of no return, their stains shaken off by knowing.
In plain words
Four phrases, and all four say the same thing.
Understanding, self, standing, devotion — all pointed one way.
The repetition is not padding. It is describing something that has stopped being divided.
Where you've felt this · in friendship
Your friend decided at twenty-two what she was going to spend her life on, and she has not wavered since. She is not rigid about it. Everything else simply arranges itself around that one thing without her having to decide again each time.
Going deeper
Four words with the same prefix, stacked in one line: understanding in that, self in that, standing in that, devoted to that.
Sanskrit can do this, and English has to spread it out. What gets lost in the spreading is the effect, which is of a person who no longer has parts pointing in different directions.
That is worth separating from fanaticism, because the two look similar from outside. The difference is what the repetition is doing here. This is not someone holding a position against pressure. It is someone in whom the question of holding has stopped arising.
Apunar-āvṛtti — non-returning. The traditional reading is release from rebirth. There is also a plainer one available: some things, once seen, cannot be unseen, and you do not go back to the version of yourself that had not seen them.
Both readings are current, and the plainer one is usable today without settling the larger question.