SB 8.24.8

kālenāgata-nidrasya
 dhātuḥ śiśayiṣor balī
mukhato niḥsṛtān vedān
 hayagrīvo ’ntike ’harat
Word for word: 
kālena — because of time (the end of Brahmā’s day); āgata-nidrasya — when he felt sleepy; dhātuḥ — of Brahmā; śiśayiṣoḥ — desiring to lie down to sleep; balī — very powerful; mukhataḥ — from the mouth; niḥsṛtān — emanating; vedān — the Vedic knowledge; hayagrīvaḥ — the great demon named Hayagrīva; antike — nearby; aharat — stole.
Translation: 
At the end of Brahmā’s day, when Brahmā felt sleepy and desired to lie down, the Vedas were emanating from his mouth, and the great demon named Hayagrīva stole the Vedic knowledge.