Requiem Masses are masses that are offered for the dead. They derive their name from the first word of the Introit, which may be traced to the Fourth Book of Esdras, one of the Apocrypha, at the passage "Expectate pastorem vestrum, requiem æternitatis dabit vobis . . . Parati estote ad præmia regni, qui lux perpetua lucabit vobis æternitatem temporis" (IV Esd., ii, 34, 35). It is also connected with a passage in Isaias, "Et requiem tibi dabit Dominus semper, et implebit splendoribus animam tuam" (Is. lxviii, 11). The Antiphon is from Psalm lxiv. The date of the adoption of this Introit is not well known, but it is found in the so-called Antiphonary of St. Gregory Come of Albino (see the edition Rome, 1691. p. 226).