Synopsis of the Books of the Bible, by John Nelson Darby, [1857-62], at sacred-texts.com
First, the perfect number of the remnant of Israel is sealed, before the providential instruments of God's judgments are allowed to act; 144,000 = 12 x 12 x 1000. They are secured for blessing according to God's purposes and set apart by Him; not yet seen in their blessings, but secured for them. Afterwards the vast multitude from among the gentiles is seen. We must remark here, there is no previous prophetic announcement of the blessing of the spared ones in the great tribulation (not the three years and-a-half of Matthew 24-this refers to Jews but that mentioned in the epistle to the church at Philadelphia). Hence this is fully given to us here, and we are distinctly told who they are. A multitude of Gentiles is seen standing not as around the throne, but before it and before the Lamb, their righteousness owned and themselves victorious. They ascribe salvation to God thus revealed, that is, to God on the throne, and to the Lamb. They belong to these earthly scenes, not to the assembly. This is answered by the angels who are around the throne, the elders, and the living creatures all together composing the heavenly part of the scene already connected with the throne; the angels surrounding the others, which form the centre and immediate circle of the throne, the white-robed multitude before it. The angels give their Amen, and pronounce the praise of their God too.
All this belonged to the white-robed multitude and the angels; only the former speak of the Lamb, who was also their salvation. The angels add their Amen to this; but praise their God. They had ascribed glory and blessing to the Lamb before; but, naturally, salvation to the Lamb was not their own part of the song. But the four living creatures and the elders do not worship here, because their own relationships were different, and these are not what are spoken of here. They are found, as far as the book goes, in Chapters 4 and 5, where they are on thrones around, and cast their crowns before the throne, and worship Him that liveth for ever and ever. They give the motives of worship according to the relationships they are in: that of the angels is with their God; of the white robed multitude, with the God of the throne and the Lamb as having the title to the government and deliverance of the earth as a present thing. That the Lamb was the Son, yea, the God who created the angels, is not the question here, but of each speaking in his own relationship, so as to bring these relationships out.
We have thus the heavenly hosts, the glorified saints, and the white-robed multitude, each in a different relationship, but the first and the last thrown in the main together the glorified saints forming a class apart. They do not worship here. But one of the elders, who have always the intelligence of God explains to the prophet who the white-robed multitude are. It formed no part of the prophetic revelation as yet, and it was not the assembly's own place. "Sir, thou knowest," says the prophet. They had come out of the great tribulation, faithful in it, their robes white in the blood of the Lamb. They were not millennial saints, that is, born in that time, and subject by birth to the responsibility of that condition (which grace had to meet). They were cleansed and owned to be so, having the consciousness of it and victory when the others began; so that they, as already cleansed and owned, are always before the throne a special class, and serve Him day and night in His temple.