In plain words
who is equal in pleasure and pain, self-established, regarding earth, stone, and gold alike, wise and equal toward the pleasant and unpleasant, blame and self-praise,
Word for word
Even in pain and pleasure, abiding in himself, to whom a clod, a stone and gold are the same, equal toward the pleasant and the unpleasant, wise, equal in blame and praise of himself,
समदुःखसुखः स्वस्थः समलोष्टाश्मकाञ्चनःतुल्यप्रियाप्रियो धीरस्तुल्यनिन्दात्मसंस्तुतिः
Other commentaries
The commentators
▸Bhagavadgītābhāṣyam
किञ्च —
समदुःखसुखः समे दुःखसुखे यस्य सः समदुःखसुखः, स्वस्थः स्वे आत्मनि स्थितः प्रसन्नः, समलोष्टाश्मकाञ्चनः लोष्टं च अश्मा च काञ्चनं च लोष्टाश्मकाञ्चनानि समानि यस्य सः समलोष्टाश्मकाञ्चनः, तुल्यप्रियाप्रियः प्रियं च अप्रियं च प्रियाप्रिये तुल्ये समे यस्य सोऽयं तुल्यप्रियाप्रियः, धीरः धीमान् , तुल्यनिन्दात्मसंस्तुतिः निन्दा च आत्मसंस्तुतिश्च निन्दात्मसंस्तुती, तुल्ये निन्दात्मसंस्तुती यस्य यतेः सः तुल्यनिन्दात्मसंस्तुतिः ॥ २४ ॥
In plain words
And there's more —
'One for whom pain and pleasure are the same' means simply this: someone who remains equally steady through pain and pleasure. 'Situated in himself' means resting quietly in his own ātman, at peace. 'One for whom a clod of earth, a stone, and gold are the same' means: a lump of dirt, a rock, a piece of gold — none of them means more to him than the others. 'One for whom the pleasant and the unpleasant are alike' means the agreeable and the disagreeable no longer pull him in different directions; he is steady, deeply intelligent. And 'one for whom blame and praise of himself are alike' means exactly what it says: whether this renunciate is criticized or praised to his face, it lands the same way — because for him, the two are simply equal.
Close to the Sanskrit
Moreover —
'One for whom pain and pleasure are equal': pain and pleasure are equal for whom — he [is] one for whom pain and pleasure are equal. 'Situated in himself': situated, established in his own ātman, serene. 'One for whom a clod, a stone and gold are equal': a clod, and a stone, and gold — clod, stone and gold are equal for whom — he [is] one for whom clod, stone and gold are equal. 'One for whom the pleasant and unpleasant are alike': the pleasant, and the unpleasant — the pleasant and unpleasant are alike, equal, for whom — he, this one, [is] one for whom the pleasant and unpleasant are alike; steady, [i.e.] possessed of understanding; 'one for whom blame and self-praise are alike': blame, and self-praise — blame and self-praise are alike for whom, [namely] for the ascetic — he [is] one for whom blame and self-praise are alike.