Bhagavad Gita Chapter 14, Verse 24

समदुःखसुखः स्वस्थः समलोष्टाश्मकाञ्चनः | तुल्यप्रियाप्रियो धीरस्तुल्यनिन्दात्मसंस्तुतिः ||

sama-duḥkha-sukhaḥ sva-sthaḥ sama-loṣṭāśma-kāñcanaḥ tulya-priyāpriyo dhīras tulya-nindātma-saṁstutiḥ

He is equal in pleasure and pain, self-controlled, regards a clod of earth, a stone, and gold as equal, is the same to the dear and the unfriendly, who is firm, and to whom censure and praise are one and the same.

Krishna continues describing the characteristics: 'Sama-duḥkha-sukhaḥ sva-sthaḥ'—equal (sama) in pleasure (sukhaḥ) and pain (duḥkha), self-controlled (sva-sthaḥ). 'Sama-loṣṭāśma-kāñcanaḥ'—regards a clod of earth (loṣṭa), a stone (aśma), and gold (kāñcanaḥ) as equal (sama). 'Tulya-priyāpriyo dhīras tulya-nindātma-saṁstutiḥ'—equal (tulya) to the dear (priya) and the unfriendly (apriyaḥ), steady (dhīraḥ), and to whom censure (nindā) and praise (ātma-saṁstutiḥ) are one and the same (tulya). This describes complete equanimity: equal response to pleasure and pain, to valuable and worthless, to friend and foe, to praise and blame. This is the mark of transcendence: you're not affected by the dualities of material existence. You remain steady regardless of external circumstances.