The day of the Lord. The same as “the day of God” (v. 12). For comment see on Acts 2:20; Phil. 1:6; 1 Thess. 5:2.
Will come. In the Greek the verb is placed in an emphatic position. The fact that the day of the Lord will come is beyond doubt.
Thief. Gr. kleptes (see on John 10:1). The same figure is used by Jesus (Matt. 24:43), by Paul (1 Thess. 5:2), and by John (Rev. 3:3; 16:15) to stress the unexpectedness of the Lord’s return. He who wishes to be saved must be right with God before the day of the Lord arrives, for there will be no opportunity for repentance on that great day.
In the night. Textual evidence favors (cf. p. 10) the omission of these words.
In the which. That is, in the day of the Lord.
The heavens. See on v. 5.
Pass away. Gr. parer chomai, “to pass away,” “to perish” (cf. Matt. 5:18; 24:35; Rev. 21:1).
With a great noise. Gr. rhoizedon, an onomatopoeic adverb indicating the noise made by birds’ wings or by an object hurtling through the air. Peter probably uses the word to represent the sound made by roaring flames.
Elements. Gr. stoicheia, “things arranged in rows,” applied to the letters of the alphabet as being set in rows; and, later, to the celestial bodies, the sun, moon, and stars (cf. on Gal. 4:3). It is probable, though not certain, that Peter here speaks of the physical elements of which our world is composed, matter that will “melt” under the cleansing fires of the last day.
Melt. Gr. luo, generally translated “to loosen,” but rendered “to dissolve” in vs. 11, 12, in the sense of “to break up,” or “to break down.” The KJV idea of “to melt” is doubtless drawn from the mention of “fervent heat.”
With fervent heat. Gr. kausod, a medical term, “to be parched with fever,” hence here and in v. 12, “to burn up.” For the association of fire and heat with Christ’s appearing see on Ps. 50:3; Mal. 4:1; 2 Thess. 1:8; cf. on Rev. 20:9; etc.
The earth ... therein. That is, all earthly things the works of man and of nature.
Burned up. Textual evidence is divided (cf. p. 10) between this reading and “shall be found.” The reading of the KJV suits the context, but the alternate reading is also possible, giving the thought that the worthlessness of earthly, material things will be discovered and displayed before the universe.