Mahabharata 13.109.63

ब्राह्मणेभ्यः परं नास्ति पावनं दिवि चेह चउपवासैस्तथा तुल्यं तपःकर्म न विद्यते

brāhmaṇebhyaḥ paraṃ nāsti pāvanaṃ divi ceha caupavāsaistathā tulyaṃ tapaḥkarma na vidyate

Our plain-language meaning of this verse is waiting for scholar review.