Commentaries:
Making and worshipping an idol is foolishness and a lie, because a manmade image can never truthfully represent the Eternal God. For a son of God, worshipping idols is irrational (Acts 17:29); to look to something physical as important or more important than God defies all wisdom. The way the world looks to physical objects is superstition (e.g., good luck charms, religious crosses, shrines).
Martin G. Collins
The Second Commandment
It is vital for us to understand that this is where the Sabbath "rest" comes from! God is the source of strength, power, and refreshment. They all come from our relationship with God within the proper keeping of the Sabbath day. He gives it to us as a gift of His grace.
He restores our energy. He gives us the power to overcome and to grow. He gives us peace of mind so that we are truly rested. He helps us to recover our strength. He enables us to live confident, hope-filled lives. He gives us good health and sound minds. "The Lord gives His beloved sleep" (Psalm 172:2). He gives us strength-restoring sleep. All of these things are gifts of grace from time well-spent in fellowship with Him, developing the relationship with Him and communicating with Him in Bible study and prayer.
How we use the Sabbath day tells Him a great deal about how we will do in His Kingdom. I fear that many of us have put the wrong emphasis on it. We tend to look at the Sabbath day as "things that we cannot do" rather than "things we can do" - truly liberating things we cannot devote time to do on the other six days of the week.
John W. Ritenbaugh
Sabbathkeeping (Part 1)
Other Forerunner Commentary entries containing Isaiah 40:29:
Amos 3:7
Matthew 24:36
1 Corinthians 13:8
1 Corinthians 13:8