Shatapatha Brahmana 11.5.6.9

11.5.6.9

tasya vā etasya brahmayajñasya catvāro vaṣaṭkārā yadvāto vāti yadvidyotate yatstanayati yadavasphūrjati tasmādevaṃvidvāte vāti vidyotamāne stanayatyavasphūrjatyadhīyītaiva vaṣaṭkārāṇāmacambaṭkārāyāti ha vai punarmṛtyum mucyate gacati brahmaṇaḥ sātmatāṃ sa cedapi prabalamiva na śaknuyādapyekaṃ devapadamadhīyītaiva tathā bhūtebhyo na hīyate

Now, for this, sacrifice to the Brahman there are four Vashat-calls,--to wit, when the wind blows, when it lightens, when it thunders, and when it rumbles whence he who knows this should certainly study when the wind is blowing, and when it lightens, or thunders, or rumbles, so as not to lose his Vashat-calls; and verily he is freed from recurring death, and attains to community of nature (or, being) with the Brahman. And should he be altogether unable (to study), let him at least read a single divine word; and thus he is not shut out from beings.