梵網經菩薩戒本疏 5.23

5.23

三、釋名者，心捨大乘故名「背正」，遵崇邪小故曰「向邪」，戒禁防此失故名為戒。

Third, regarding the explanation of the name: because the mind abandons the Mahāyāna, it is called "turning one's back on the orthodox"; because one venerates and respects the heterodox and Hīnayāna, it is called "heading toward the heterodox." The precept restrains and guards against this fault; hence it is called a precept.