[He did this] to fulfill His plan at the proper time, by bringing together everything [in the universe] under Christ's headship --- things both in heaven and on earth.

The One who descended [i.e., from heaven to earth] is the same One [i.e., Christ] who also ascended high above the all the heavens, so that He could fill the entire universe [with His presence]).

[but] during these final days He has spoken to us through His Son [Note: This period refers to the Christian age (See Acts 2:14-36)], whom He appointed to be heir of all things [and] through whom He created the universe. [See John 1:3; Col. 1:16].

By [having] faith, we understand that the universe was formed by God's word [See Gen. 1:1-27], so that what is seen has not been made out of what is visible.

Now the words, "once more" indicate the removing of what can be shaken --- that is, the created universe --- so that those things which cannot be shaken will remain. [Note: These "things" have been variously interpreted to be eternal truth, the heavenly kingdom, the new heavens and earth, etc.].

But the day of the Lord will come as a thief [i.e., unexpectedly]. At that time the heavens will pass away with a loud noise and the elements [Note: This refers either to the heavenly bodies or to the material components of the universe], will be dissolved with intense heat. And the earth and its works [i.e., its activities] will be burned up. [Note: Some translations render this phrase as it is in some ancient manuscripts, "will be disclosed," or "will be laid bare"].