Canto 1 - Boyhood
Bāla-kāṇḍa
Chapter 16: Daśaratha Benedicted
Text 1.16.9

स चाप्यपुत्रो नृपतिस्तस्मिन्काले महाद्युतिः।
अयजत्पुत्रियामिष्टिं पुत्रेप्सुररिसूदनः॥

sa cāpy aputro nṛ-patis tasmin kāle mahā-dyutiḥ
ayajat
putriyām iṣṭiṁ putrepsur ari-sūdanaḥ

saḥ ca api = the; aputraḥ = childless; nṛ-patiḥ = king; tasmin = at that; kāle = time when the Supreme Personality of Godhead wanted to incarnate; mahā-dyutiḥ = of great splendor; ayajat = was conducting sacrifice; putriyām = the Putrīya; iṣṭim = Iṣṭi; putra-īpsuḥ = desiring sons; ari-sūdanaḥ = the killer of his enemies.

At that time when the Supreme Personality of Godhead wanted to incarnate, the childless king of great splendor, the killer of his enemies, was conducting the Putrīya Iṣṭi sacrifice desiring sons.