KAṬHA UPANISHAD · 1.3.17

य इमं परमं गुह्यं श्रावयेद् ब्रह्मसंसदि ।
प्रयतः श्राद्धकाले वा तदानन्त्याय कल्पते ।
तदानन्त्याय कल्पत इति ॥ १७॥

ya imaṃ paramaṃ guhyaṃ śrāvayed brahmasaṃsadi ।
prayataḥ śrāddhakāle vā tadānantyāya kalpate ।
tadānantyāya kalpata iti ॥ 17॥

He who being pure recites this supreme secret at the time of the Shraddha in the assembly of the Brahmins, that turns for him to infinite existence.