SB 5.18.34
uttaresu ca kurusu bhagavan yajña-purusah krta-varaha-rupa aste tam tu devi haisa bhuh saha kurubhir askhalita-bhakti-yogenopadhavati imam ca paramam upanisadam avartayati.
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Sukadeva Gosvami said: Dear King, the Supreme Lord in His boar incarnation, who accepts all sacrificial offerings, lives in the northern part of Jambudvipa. There, in the tract of land known as Uttarakuru-varsa, mother earth and all the other inhabitants worship Him with unfailing devotional service by repeatedly chanting the following Upanisadic mantra.