Canto 1 - Boyhood
Bāla-kāṇḍa
Chapter 17: Brahmā Orders the Demigods to Incarnate and Assist Rāma
Text 1.17.1

पुत्रत्वं तु गते विष्णौ राज्ञस्तस्य महात्मनः।
उवाच देवताः सर्वाः स्वयम्भूर्भगवानिदम्॥

putratvaṁ tu gate viṣṇau rājñas tasya mahātmanaḥ
uvāca
devatāḥ sarvāḥ svayambhūr bhagavān idam

putratvam tu gate = had become the sons; viṣṇau = when Lord Viṣṇu; rājñaḥ = king; tasya = of the; mahā-ātmanaḥ = greatly intelligent; uvāca = spoke; devatāḥ = the demigods; sarvāḥ = to all; svayambhūḥ = Svayambhū; bhagavān = Lord; idam = the following.

When Lord Viṣṇu had become the sons of the greatly intelligent king, Lord Svayambhū (Brahmā) spoke to all the demigods.

After the disappearance of Lord Viṣṇu, two events took place: (1) the appearance of the person from the fire with the pāyasa, and (2) Lord Brahmā’s instructions to the demigods to incarnate. Having described the first event and other events related to it, sage Vālmīki describes the second event and events subsequent to it in this chapter.

Bhagavān (“Lord” in this context) here indicates that Lord Brahmā was aware of his next duty.