Śatapatha Brāhmaṇa ("of a hundred paths") 2.3.1.25

2.3.1.25

ātmaiva bhūtam | addhā hi tadyadbhūtamaddho tadyadātmā prajaiva bhaviṣyadanaddhā hi tadyadbhaviṣyadanaddho tadyatprajā

The past is the self, for certain is that which is past, and certain also is that which is a self. The future, on the other hand, is progeny; for uncertain is that which is to be, and uncertain also is progeny.