He (Krsna was born of Devaki but according to His original plan He went to Vrndavana and after eleven years) would return to kill Kamsa. Because Kamsa did not know this, he believed Yogamaya's statement that Krsna was born elsewhere, not of Devaki

Expressions researched:
"He would return to kill Kaṁsa. Because Kaṁsa did not know this, he believed Yogamāyā's statement that Kṛṣṇa was born elsewhere, not of Devakī"

Srimad-Bhagavatam

SB Canto 10.1 to 10.13

Kṛṣṇa was born the son of Devakī, but according to the Lord's original plan, as prophesied to Brahmā, He went to Vṛndāvana to give pleasure to mother Yaśodā and Nanda Mahārāja and other intimate friends and devotees for eleven years. Then He would return to kill Kaṁsa. Because Kaṁsa did not know this, he believed Yogamāyā's statement that Kṛṣṇa was born elsewhere, not of Devakī.

SB 10.4.29, Translation and Purport

After that night passed, Kaṁsa summoned his ministers and informed them of all that had been spoken by Yogamāyā (who had revealed that He who was to slay Kaṁsa had already been born somewhere else).

The Vedic scripture Caṇḍī describes māyā, the energy of the Supreme Lord, as nidrā: durgā devī sarva-bhūteṣu nidrā-rūpeṇa samāsthitaḥ. The energy of Yogamāyā and Mahāmāyā keeps the living entities sleeping in this material world in the great darkness of ignorance. Yogamāyā, the goddess Durgā, kept Kaṁsa in darkness about Kṛṣṇa's birth and misled him to believe that his enemy Kṛṣṇa had been born elsewhere. Kṛṣṇa was born the son of Devakī, but according to the Lord's original plan, as prophesied to Brahmā, He went to Vṛndāvana to give pleasure to mother Yaśodā and Nanda Mahārāja and other intimate friends and devotees for eleven years. Then He would return to kill Kaṁsa. Because Kaṁsa did not know this, he believed Yogamāyā's statement that Kṛṣṇa was born elsewhere, not of Devakī.