Bhagwad Gita
Chapter 7, Verse 11
बलं बलवतां चाहं कामरागविवर्जितम्।
धर्माविरुद्धो भूतेषु कामोऽस्मि भरतर्षभ।।7.11।।
I am the strength of the strong, devoid of passion and desire. I am sex life which is not contrary to religious principles, O Lord of the Bharatas [Arjuna].