Shatapatha Brahmana 2.3.3.6

2.3.3.6

tasmādetadṛṣiṇābhyanūktaṃ | śataminnu śarado anti devā yatrā naścakrā jarasaṃ tanūnām putrāso yatra pitaro bhavanti mā no madhyā rīriṣatāyurgantoriti putro hyeṣa santsa punaḥ pitā bhavatyetannu tadyasmādagnī ādadhīta

Hence it has been said by the Rishis (Rig-veda I, 89, 9), 'A hundred autumns (may there he) before us, O gods, during which ye complete the life-time of our bodies, during which sons become fathers! do not cut us off, midway, from reaching the full term of life!' for he (Agni) who is the son, now in his turn becomes the father: this, then, is why one must establish the fires.