The great personality Brahmā, with great attention and concentration of the mind, studied the Vedas three times, and after scrutinizingly examining them, he ascertained that attraction for the Supreme Personality of Godhead Śrī Kṛṣṇa is the highest perfection of religion.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
भगवान् ब्रह्म कार्त्स्न्येन त्रिरन्वीक्ष्य मनीषया । तदध्यवस्यत्कूटस्थो रतिरात्मन् यतो भवेत्
bhagavān brahma kārtsnyena triranvīkṣya manīṣayā | tadadhyavasyatkūṭastho ratirātman yato bhavet
SB 2.2.34