Bhagavad Gita 18.8
To avoid an action out of fear of physical suffering, as it is likely to be painful, is to act out of passion, and the benefit of renunciation will not be gained.
दुःखमित्येव यत्कर्म कायक्लेशभयात्त्यजेत्।स कृत्वा राजसं त्यागं नैव त्यागफलं लभेत्॥duḥkhamityeva yatkarma kāyakleśabhayāttyajet|sa kṛtvā rājasaṃ tyāgaṃ naiva tyāgaphalaṃ labhet||
English translation (above): Shri Purohit Swami (1935), public domain. Sanskrit text via github.com/gita/gita (Unlicense).