Everyone gets weary, and everyone must rest. Even in Eden before sin came into the world there was a weekly day of rest, and each day of work in the Garden was followed by a night of rest in sleep. The Lord Jesus Christ, in the days of His sinless human flesh, occasionally became "wearied with his journey" (John 4:6) and had to rest. On one occasion, He was so weary that during a violent storm on the Sea of Galilee He was "asleep on a pillow" (Mark 4:38), while the disciples tried to keep their ship from destruction. He once advised these fretful and busy disciples to "come ye yourselves apart into a desert place, and rest a while" (Mark 6:31). We sometimes need to come apart before we fall apart!

In the New Jerusalem, with our new bodies, we perhaps will not need rest and sleep, for "there shall be no night there" (Revelation 22:5). In our present frail tents of clay, however, we do need rest, for God made us so. In one area of life, on the other hand, we are twice admonished to "not be weary in well doing" (Galatians 6:9; 2 Thessalonians 3:13).

And when we do get weary, and perhaps are not yet able to stop and rest, we can draw on God’s strength, for He "fainteth not, neither is weary." "He that keepeth Israel shall neither slumber nor sleep" (Psalm 121:4). "Even the youths shall faint and be weary, and the young men shall utterly fall: But they that wait upon the LORD shall renew their strength; they shall mount up with wings as eagles; they shall run, and not be weary; and they shall walk, and not faint" (Isaiah 40:30-31). HMM

http://www.icr.org/article/6965/