Bhagavad Gita 18.42
Serenity, self-restraint, austerity, purity, forgiveness, uprightness, knowledge, wisdom, and faith in God—these constitute the duty of a spiritual teacher.
शमो दमस्तपः शौचं क्षान्तिरार्जवमेव च।ज्ञानं विज्ञानमास्तिक्यं ब्रह्मकर्म स्वभावजम्॥śamo damastapaḥ śaucaṃ kṣāntirārjavameva ca|jñānaṃ vijñānamāstikyaṃ brahmakarma svabhāvajam||
English translation (above): Shri Purohit Swami (1935), public domain. Sanskrit text via github.com/gita/gita (Unlicense).