Bhagavatapurana 3.1.10

3.1.10

yadopahūto bhavanaṃ praviṣṭo mantrāya pṛṣṭaḥ kila pūrvajena /
athāha tan mantra-dṛśāṃ varīyān yan mantriṇo vaidurikaṃ vadanti //

10. When invited by his elder brother, he (Vidura) came into the palace and was asked for advice, Vidura the foremost of counsellors immediately offered that counsel which ministers (of all times) speak of as ‘Vidura’s Advice’ (that is, it has ever since become the model of good counsel for those who should fill the place of ministers.)