Canto 1 - Boyhood
Bāla-kāṇḍa
Chapter 34: Satyavatī, Viśvāmitra’s Elder Sister
Text 1.34.4
एवम् उक्त्वा कुशो राम कुशनाभं महीपतिम्।
जगामाकाशमाविश्य ब्रह्मलोकं सनातनम्॥
evam uktvā kuśo rāma kuśanābhaṁ mahī-patim
jagāmākāśam āviśya brahma-lokaṁ sanātanam
evam uktvā = having spoken thus; kuśaḥ = Kuśa; rāma = O Rāma; kuśanābham mahī-patim = to King Kuśanābha; jagāma ākāśam āviśya = entered the skies and went; brahma-lokam sanātanam = to the eternal abode of Lord Brahmā.
O Rāma, having spoken thus to King Kuśanābha, Kuśa entered the skies and went to the eternal abode of Lord Brahmā.
From this it is understood that Kuśa, who constantly resides at Brahmaloka, had descended to earth in order to bless his son Kuśanābha.