Praśna Upaniṣad ("Six Questions") 1.2

1.2

tānha sa ṛṣiruvāca bhūya eva tapasā brahmacaryeṇa śraddhayā saṃvatsaraṃ saṃvatsyatha
yathākāmaṃ praśnānpṛcchata yadi vijñāsyāmaḥ sarvaṃha vo vakṣyāma iti

2. To them then that seer (ṛṣi) said: ‘Dwell with me (saṃvatsyatha) a year (saṃvatsara) more, with austerity (tapas), chastity (brahmacarya), and faith (śraddhā). Then ask what questions you will. If we know, we will tell you all.’