They bound themselves by a sacred lay and oath.
Holland.
Lay (?), a. [OF. lai, lais, prob. of Celtic origin; cf. Ir. laoi,
laoidh, song, poem, OIr. laoidh poem, verse; but cf. also AS. lc play,
sport, G. leich a sort of poem (cf. Lake to sport). &?;.] 1. A song; a
simple lyrical poem; a ballad. Spenser. Sir W. Scott.