Brahmacharya is the supreme penance

Lord Siva said:

न तपस्तप इत्याहुर्ब्रह्मचर्यं तपोत्तमम् | ऊर्ध्वरेता भवेद्यस्तु स देवो न तु मानुषः ||

"Celibacy alone is the supreme penance. Of course, other penances (such as keeping fast and silence etc ...) are good in their place, but they are all inferior to Brahmacharya. That Urdhvareta saint who has done penance over the restraint of the sexual organ is not a human-being but God."

Brahmacharya is also hailed in Jain scriptures.