Then Vīrabhadra saw the wooden device in the sacrificial arena by which the animals were to have been killed. He took the opportunity of this facility to behead Dakṣa.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
दृष्ट्वा संज्ञपनं योगं पशूनां स पतिर्मखे । यजमानपशोः कस्य कायात्तेनाहरच्छिरः
dṛṣṭvā saṃjñapanaṃ yogaṃ paśūnāṃ sa patirmakhe | yajamānapaśoḥ kasya kāyāttenāharacchiraḥ
SB 4.5.24