Thus situated in the renounced order from the beginning of their lives, all three of them completely controlled the activities of their senses and thus became great saints. They concentrated their minds always upon the lotus feet of the Supreme Personality of Godhead, who is the resting place of the totality of living entities and who is therefore celebrated as Vāsudeva. Lord Vāsudeva is the only shelter of those who are actually afraid of material existence. By constantly thinking of His lotus feet, these three sons of Mahārāja Priyavrata became advanced in pure devotional service. By the prowess of their devotional service, they could directly perceive the Supreme Personality of Godhead, who is situated in everyone’s heart as the Supersoul, and realize that there was qualitatively no difference between themselves and Him.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
तस्मिन्नु ह वा उपशमशीलाः परमर्षयः सकलजीव- निकायावासस्य भगवतो वासुदेवस्य भीतानां शरणभूतस्य श्रीमच्चरणारविन्दाविरतस्मरणाविगलितपरमभक्तियोगा- नुभावेन परिभावितान्तर्हृदयाधिगते भगवति सर्वेषां भूताना- मात्मभूते प्रत्यगात्मन्येवात्मनस्तादात्म्यमविशेषेण समीयुः
tasminnu ha vā upaśamaśīlāḥ paramarṣayaḥ sakalajīva- nikāyāvāsasya bhagavato vāsudevasya bhītānāṃ śaraṇabhūtasya śrīmaccaraṇāravindāviratasmaraṇāvigalitaparamabhaktiyogā- nubhāvena paribhāvitāntarhṛdayādhigate bhagavati sarveṣāṃ bhūtānā- mātmabhūte pratyagātmanyevātmanastādātmyamaviśeṣeṇa samīyuḥ
SB 5.1.27