Mahabharata 3.80.78

तस्मिंस्तीर्थवरे स्नात्वा शुचिः प्रयतमानसःअग्निष्टोमातिरात्राभ्यां फलं प्राप्नोति मानवः

tasmiṃstīrthavare snātvā śuciḥ prayatamānasaḥagniṣṭomātirātrābhyāṃ phalaṃ prāpnoti mānavaḥ

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