Charles H. Spurgeon on Psalms 149:5

Let the saints be joyful in glory: let them sing aloud upon their beds. At what time soever God is pleased to inspire his grace and comfort into us, we ought to rejoice therein, and by night on the bed to seek him whom our soul loveth; abridging that time of rest and ease, that it may become as beneficial unto us as the day itself. David was not satisfied by offering the sacrifice of thanksgiving in the courts of the Lord's house, and paying his vows in the presence of all the people; but in the night also he would continue his song of God's mercy. Like that excellent bird, the nightingale, which is never weary nor spent by continuing her delightful notes, so this sweet singer of Israel was incessant in praising the Lord; not giving sleep to his eyes until he had blessed his holy name. In time of affliction he made his bed to swim, praying unto the Lord to return and deliver his soul. Now in prosperity he gives thanks for the blessings he doth receive. When our bones are vexed, and our sleep departeth from us, we pray unto God to deal mercifully with us; but when our diseases are healed, we do not return to give thanks, being soon overtaken with heaviness and security. And yet David did endeavour to watch in the night, that he might sing praise unto the Lord. He did not then only meditate in the law of God, when he could not take any rest (as Ahasuerus had the book of the records of the Chronicles read before him, when he could not sleep); for now he might lie down in peace, and sleep, when God made him to dwell in safety. Much less did he intend to procure sleep by a sinister performance of any good duty, like those who, by singing, or reading, or hearing, or meditating, will have an unworthy aim to bring themselves asleep. David saith, "Let the saints sing aloud upon their beds": thereby to testify their cheerful devotion, and also to chase away the spirit of slumber. —William Bloys, in "Meditations upon the xlii. Psalm," 1632.