Kena Upanishad 3.7

अथ वायुमब्रुवन्वायवेतद्विजानीहि
किमेतद्यक्षमिति तथेति ॥ ७॥

atha vāyumabruvanvāyavetadvijānīhi
kimetadyakṣamiti tatheti .. 7..

Then they addressed Vāyu: “O Vāyu, please ascertain this, who this yaksha is.” “Yes”, said Vāyu.