Revelation 20:3
And cast him into the bottomless pit, and shut him up, and set a seal upon him, that he should deceive the nations no more, till the thousand years should be fulfilled: and after that he must be loosed a little season. (Revelation 20:3)
Loosed.
 This represents the reverse of the binding of the devil at the second coming of Christ. Satan is again to be in the position to deceive men, to work his will with them in opposition to God. It was the depopulation of the earth that terminated his deceptive work. His loosing will therefore be accomplished by a repopulation of the earth, an event brought about by the resurrection of the wicked at the close of the thousand years (see on v. 5). These newly resurrected ones will be subject to his deceptions as he plans his final test of strength with Jehovah.
Must.
Gr. dei “it is necessary.” Dei suggests necessity based upon moral and ethical reasons. Here it is a necessity because God wills that it shall be so, as a part of His divine plan.
Deceive the nations.
 Satan’s work of deception will be cut short by the depopulation of the earth. There will be no one whom he can deceive (see on v. 1).
Set a seal.
 Gr. sphragizō, “to seal.” For the function of ancient seals see on ch. 7:2. The present seal may be compared with that placed on the tomb of Jesus (Matt. 27:66). The sealing symbolizes that Satan will be effectively restrained for the period indicated.
Bottomless pit.
 See on v. 1.
A little season.
Or, “a little time.” How long this “little” time will be, we are not informed. It will be time enough for Satan to organize the resurrected wicked for an assault upon the New Jerusalem.