淨名經集解關中疏 1.111

1.111

夜叉　肇曰。秦言輕捷有三種。一在地。二在虛空。三天夜叉。居下二天守天城門閤。

"Yakṣas." Sengzhao says: "In the language of Qin, this means 'nimble and swift'. There are three kinds: first, those on earth; second, those in space; third, heavenly yakṣas, who dwell in the lower two heavens guarding the gates and towers of the celestial cities."