Praśna Upaniṣad ("Six Questions") 1.8.p2

1.8.p2

tadyeha vaitadiṣṭāpūrte kṛtamityupāsate

Now, those, verily, indeed, who worship, thinking "Sacrifice and merit are our work (*kṛta*)!"—they win only the lunar world. They, indeed, return hither again. Therefore those seers (*ṛṣi*) who are desirous of offspring go the Southern course. This matter (*rayi*) verily it is, that leads to the fathers (*pitṛyāṇa*).