The works of Ādi Śaṅkarācārya

Muṇḍakopaniṣadbhāṣyam

Verse 16

प्रणवो धनु' शरो ह्यात्मा ब्रह्म तल्लक्ष्यमुच्यते ।अप्रमत्तेन वेद्धव्य शरवत्तन्मयो भवेत् ॥ ४ ॥

In plain words

Om is the bow, the self is the arrow, and Brahman is called the target. It must be hit with an alert and focused mind, until one becomes completely one with it, just as an arrow merges into its mark.

Close to the Sanskrit

Pranava is the bow, the soul indeed is the arrow, Brahman is said to be the target. It is to be pierced by an attentive person; one should become absorbed in it like an arrow.