In the view of the authors, going to sleep should be treated as a daily memento mori, a reminder of the inevitability of death. The second and third prayers in particular draw out this aspect of night and slumber.
In addition, the third prayer echoes the traditional Collect for Grace that is used at the beginning of the day, and thus bookends it. The two together make a salutary way of opening and closing the day. (This is the second time we have caught an echo of this prayer.)
God did rest the seventh day from all His works.–Heb. iv. 4.
There remaineth therefore a rest to the people of God.–Heb.iv. 9.
Blessed are the dead who die in the Lord from henceforth; yea, saith the Spirit, they may rest from their labors, and their works do follow them.–Rev. xiv. 13.
Behold, he that keepeth Israel, shall neither slumber nor sleep. The Lord is they keeper; the Lord is thy shade upon thy right hand.–Ps. cxxi. 4, 5.
He shall give his angels charge over thee, to keep thee in all thy ways.–Ps. xci. 11.
He that dwelleth in the secret places of the Most High, shall abide under the shadow of the Almighty. I will say of the Lord, He is my refuge, my fortress, my God; in him will I trust.–Ps. xci. 1, 2.
Though I walk through the valley of the shadow of death, I will fear no evil; for thou art with me; thy rod and thy staff they comfort me.–Ps. xxiii. 4.
Whom have I in heaven but thee! And there is none upon earth that I desire besides thee.–Ps. lxxiii. 25.
I WILL lay me down in peace and take my rest in Thy name, O Lord, who makest me to dwell in safety. Keep me from sin and harm; refresh me with wholesome sleep, raise me up again to the praise of Thy name, and bring me at last to life eternal. Amen.
INTO Thy hands, O Lord and Keeper of Israel, I commend my body, soul, and spirit. Defend me from the terrors of the night, and preserve me from all evil. Keep me mindful of the vanity of life, the certainty of death, and the judgment to come, and prepare me for a happy end, through Jesus Christ our Savior. Amen.
MOST MERCIFUL FATHER, who hast safely brought me to the end of this day, take me under the wings of Thy protection for the coming night. Defend my body from harm, and my soul from sin. Keep me mindful of my end; and when heart and flesh fail, be Thou the strength of my heart, and my portion for ever. Amen. 1