The works of Ādi Śaṅkarācārya

Muṇḍakopaniṣadbhāṣyam

Verse 2

यदा लेलायते ह्यर्चिःसमिद्धे हव्यवाहने ।तदाज्यभागावन्तरे-णाहुतीं प्रतिपादयेत् ॥ २ ॥

In plain words

When the flame flickers within the brightly blazing fire, right between the two butter-offerings one should pour the oblation.

Close to the Sanskrit

When indeed the flame flickers in the well-kindled bearer of oblations, then between the two portions of ghee one should offer the oblation.