Canto 1 - Boyhood
Bāla-kāṇḍa
Chapter 11: Daśaratha Brings Ṛśyaśṛṅga to Ayodhyā
Text 1.11.9

यज्ञार्थं प्रसवार्थं च स्वर्गार्थं च जनेश्वरः।
लभते च स तं कामं विप्रमुख्याद्विशां पतिः॥

yajñārthaṁ prasavārthaṁ ca svargārthaṁ ca janeśvaraḥ
labhate
ca sa taṁ kāmaṁ vipra-mukhyād viśāṁ patiḥ

yajna-artham = for the sake of the yajña; prasava-artham ca = so that he would have children; svarga-artham ca = for the sake of attaining heaven; jana-iśvaraḥ = king of men; labhate ca = will be able to perform; saḥ = that; tam = that; kāmam = desire-fulfilling sacrifice; vipra-mukhyāt = through that chief of the brāhmaṇas; viśām = of the vaiśyas; patiḥ = the Lord.

That king of men, the Lord of the vaiśyas, will be able to perform that desire-fulfilling sacrifice through that chief of the brāhmaṇas for the sake of the yajña so that he would have children for the sake of attaining heaven.

Why did he accept Ṛśyaśṛṅga? To perform the sacrifice—the Putrakāmeṣṭi sacrifice to obtain sons to attain heaven.1 A person who does not have a son does not have a superior destination in his next life, according to the Śruti [1].

[1] nāputrasya loko ’sti.

1 Svarga here indicates the supreme heaven of Vaikuṇṭha that Lord Rāma attained after His manifest presence on earth.