Srimad-Bhagavatam: Canto 5 - Chapter 1 - Verse 34
Sanskrit:
उत्तरेषु च कुरुषु भगवान् यज्ञपुरुष: कृतवराहरूप आस्ते तं तु देवी हैषा भू: सह कुरुभिरस्खलितभक्तियोगेनोपधावति इमां च परमामुपनिषदमावर्तयति ॥ ३४ ॥
ITRANS:
uttareṣu ca kuruṣu bhagavān yajña-puruṣaḥ kṛta-varāha-rūpa āste taṁ tu devī haiṣā bhūḥ saha kurubhir askhalita-bhakti-yogenopadhāvati imāṁ ca paramām upaniṣadam āvartayati.
Translation:
Śukadeva Gosvāmī said: Dear King, the Supreme Lord in His boar incarnation, who accepts all sacrificial offerings, lives in the northern part of Jambūdvīpa. There, in the tract of land known as Uttarakuru-varṣa, mother earth and all the other inhabitants worship Him with unfailing devotional service by repeatedly chanting the following Upaniṣadic mantra.