Eternal rest grant unto him, O Lord...
and let perpetual light shine upon him.

J.R.R. Tolkien went to his reward on September 2, 1973, at the age of eighty-one.
Here is the Oratio of the Tridentine Mass for the Dead...

Inclina, Domine, aurem tuam ad preces nostras, quibus misericordiam tuam supplices deprecamur: ut animam famuli tui, John Ronald Reuel , quam de hoc saeculo migrare jussisti; in pacis ac lucis regione constituas, et Sanctorum tuorum jubeas esse consortem. Per Dominum Nostrum Jesum Christum Filium Tuum, Qui tecum vivit et regnat in unitate Spiritus Sancti Deus
C: Per omnia saecula saeculorum.
R: Amen.

And a translation of the same....

C: Incline Thy ear, O Lord, to the prayers with which we suppliantly entreat Thy mercy, and do Thou, in a place of peace and rest, establish the soul of Thy servant, John Ronald Reuel, whom Thou hast called out of this world; and cause him to be joined to the fellowship of Thy saints. Through Our Lord Jesus Christ, Thy Son, Who being God, lives and reigns with Thee in the unity of the Holy Ghost
C: For ever and ever.
R: Amen.

Eru gala, Professor. Uireb sed.