In plain words
Sages whose impurities are exhausted, whose doubts are cut, who are self-controlled and delight in the welfare of all beings, attain Brahma-nirvāṇa.
Word for word
The ṛṣis attain Brahma-nirvāṇa, their impurities worn away, their doubts cut, self-controlled, delighting in the welfare of all beings.
The commentators
Bhagavadgītābhāṣyam
किञ्च —
लभन्ते ब्रह्मनिर्वाणं मोक्षम् ऋषयः सम्यग्दर्शिनः संन्यासिनः क्षीणकल्मषाः क्षीणपापाः निर्दोषाः छिन्नद्वैधाः छिन्नसंशयाः यतात्मानः संयतेन्द्रियाः सर्वभूतहिते रताः सर्वेषां भूतानां हिते आनुकूल्ये रताः अहिंसका इत्यर्थः ॥ २५ ॥
In plain words
And there is more —
They reach brahmanirvāṇa — which is to say, liberation. The ṛṣis: those who see things as they are, who have laid everything down. Their taint worn away — meaning their sins are used up, and no fault is left in them. Their dividedness cut through — meaning their doubts are cut through. Their self held in — meaning their senses are held in. Devoted to the welfare of all beings — devoted to what is good for every being, what goes with them rather than against them; they harm no one. That is the sense of it.
Close to the Sanskrit
And what more —
They attain brahmanirvāṇa — liberation. The ṛṣis: those who see rightly, the renunciates. Those whose taint is worn away: those whose sins are worn away, the faultless. Those whose dividedness is cut through: those whose doubts are cut through. Those whose self is held in: those whose senses are restrained. Devoted to the welfare of all beings: devoted to the welfare — the favourableness — of all beings, that is, those who do no harm. Such is the meaning.