O Maharaja Pariksit, descendant of King Bharata, Vasudeva could understand that this child was the Supreme Personality of Godhead, Narayana. Having concluded this without a doubt, he became fearless - SB 10.3.12

Expressions researched:
"O Mahārāja Parīkṣit, descendant of King Bharata, Vasudeva could understand that this child was the Supreme Personality of Godhead, Nārāyaṇa. Having concluded this without a doubt, he became fearless"

Srimad-Bhagavatam

SB Canto 10.1 to 10.13

O Mahārāja Parīkṣit, descendant of King Bharata, Vasudeva could understand that this child was the Supreme Personality of Godhead, Nārāyaṇa. Having concluded this without a doubt, he became fearless. Bowing down with folded hands and concentrating his attention, he began to offer prayers to the child, who illuminated His birthplace by His natural influence.

SB 10.3.12, Translation and Purport

O Mahārāja Parīkṣit, descendant of King Bharata, Vasudeva could understand that this child was the Supreme Personality of Godhead, Nārāyaṇa. Having concluded this without a doubt, he became fearless. Bowing down with folded hands and concentrating his attention, he began to offer prayers to the child, who illuminated His birthplace by His natural influence.

Struck with such great wonder, Vasudeva now concentrated his attention on the Supreme Personality of Godhead. Understanding the influence of the Supreme Lord, he was surely fearless, since he understood that the Lord had appeared to give him protection (gata-bhīḥ prabhāva-vit). Understanding that the Supreme Personality of Godhead was present, he appropriately offered prayers as follows.