William Gouge, Sabbath’s Sanctification:
A. Such as our weak bodies do stand in need of. Exod. 12:16; Matt. 12:1.
Man by sin hath brought many infirmities upon his body. By them is he much disabled and hindered from performing good duties. The Lord therefore every way endeavouring with his goodness to overcome man’s wretchedness, hath by his providence afforded him sufficient means to support and redress his infirmities. These means God is willing that man should use at all times, on all occasions, so far forth as may be needful and useful for him. The Lord is not like that cruel tyrant who laid upon the Israelites, whom he held in hard bondage, as much as they could do, if not more, and yet would not afford them ordinary means to do it. He rather will have his work intermitted, than man oppressed thereby.
26. Q. What are those particulars which our weak bodies do most need?
A. 1. Sleep. Eccl. 5:12.
2. Food. Luke 14:1.
3. Apparel. 2 Sam. 12:20.
4. All other occasional helps. Mark 2:3, 4.
27. Q. Why is sleep requisite?
A. If we have not seasonable sleep the night immediately before the Sabbath (the latter part whereof, namely from midnight to the time we rise, is part of the Sabbath) the duties of the day will be so drousily performed (if at all they be performed) as they cannot be acceptable to God, nor advantageable to our spiritual edification. Sleep doth much refresh our drowsy bodies, and cheer our dull spirits: and so make us much better perform the duties of the Sabbath. Therefore sleep is said to be sweet, Eccl. 5:12.
81 Q. What ninth motive?
A. The temporal benefit of it. Deut. 5:14.
Surely a day’s rest in every week is very needful and useful for man and beast: especially for such as labour all the six days. Experience gives good proof thereof. Howsoever such as on no day take any great pains find no such benefit thereby, yet others do. And the wise God saw it to be so. For which end he expressly commanded that the beast should rest (Exod. 20:10). Now the beast can reap no other than a temporal benefit. There is therefore a temporal benefit thence arising. Some masters are so covetous and gripulous, as if there were not a seventh day for rest set apart, they would never afford any day’s rest to servants or cattle: but so weary them, as their strength would quickly be exhausted. It remains then that as the rest of every night, so the rest of every seventh day, is useful and needful: and a great temporal good is thereby brought to man and beast.
Source: http://www.puritanboard.com/showthread.php/90810-Physical-Rest-on-the-Lord-s-Day, Comment #22