Śatapatha Brāhmaṇa ("of a hundred paths") 1.7.2.4

1.7.2.4

atha yadeva prajāmiceta | tena pitṛbhya ṛṇaṃ jāyate taddhyebhya etatkaroti yadeṣāṃ saṃtatāvyavacinnā prajā bhavati

And further, inasmuch as he is bound to wish for offspring, for that reason he is born as (owing) a debt to the fathers: hence when there is (provided by him) a continued, uninterrupted lineage, it is for them that he does this.