Srimad-Bhagavatam: Canto 10 - Chapter 1 - Verse 15
य इदं लीलया विश्वं सृजत्यवति हन्ति च ।चेष्टां विश्वसृजो यस्य न विदुर्मोहिताजया ॥ १५ ॥
ya idaṁ līlayā viśvaṁsṛjaty avati hanti caceṣṭāṁ viśva-sṛjo yasyana vidur mohitājayā
“It is the Supreme Lord who creates, maintains and destroys this universe simply as His pastime. The cosmic creators cannot even understand His purpose, bewildered as they are by His illusory Māyā.
The use of the singular yaḥ, “He who,” indicates that the frequent references to “the two Lords, Kṛṣṇa and Rāma,” do not compromise the firm principle of monotheism expressed in the Śrīmad-Bhāgavatam. As explained in many Vedic literatures, the one Supreme Lord expands Himself into innumerable forms, yet He remains the one and almighty God. For example, we have this statement in the Brahma-saṁhitā (5.33): advaitam acyutam anādir ananta-rūpam. “The one Supreme Lord is infallible and beginningless, and He expands Himself into innumerable manifest forms.” Out of regard for the spirit of the Lord’s pastimes, in which He expands Himself and appears as His own older brother, Balarāma, the Bhāgavatam here refers to “the two Lords.” But the “bottom line” is that there is one Supreme Godhead, one Absolute Truth, who appears in His original form as Kṛṣṇa.