Angels of God ascending and descending upon the Son of man.

Jesus saw Nathan'a-el coming to him, and said of him, "Behold, an Israelite indeed, in whom is no guile!"

Nathan'a-el said to him, "How do you know me?" Jesus answered him, "Before Philip called you, when you were under the fig tree, I saw you."

Nathan'a-el answered him, "Rabbi, you are the Son of God! You are the King of Israel!"

Jesus answered him, "Because I said to you, I saw you under the fig tree, do you believe? You shall see greater things than these."

And he said to him, "Truly, truly, I say to you, you will see heaven opened, and the angels of God ascending and descending upon the Son of man."

John 1: 47 - 51

Angels rejoice over one sinner who repents

Just so, I tell you, there is joy before the angels of God 

over one sinner who repents.

Luke 15:10

The angels of God rejoices over those who repent on earth. They see the guilt and danger of people; they know what God has done for the race, and they rejoice at the recovery of any from the guilt and ruins of sin.

They rejoice at his repentance because it recovers him back to the love of God, and because it will save him from eternal death.

The word may refer to angels as well as to people.

There are no "just" people on earth who need no repentance, Ecclesiastes 7:20; Psalm 14:2-3; Romans 3:10-18.

Our Saviour did not mean to imply that there were any such. He was speaking of what took place "in heaven," or among "angels," and of "their" emotions when they contemplate the creatures of God; and he says that "they" rejoiced in the repentance of one "sinner" more than in the holiness of many who had not fallen.

We are not to suppose that he meant to teach that there were just ninety-nine holy angels to one sinner. He means merely that they rejoice more over the "repentance" of one sinner than they do over many who have not fallen.

By this he vindicated his own conduct.

The Jews did not deny the existence of angels. They would not deny that their feelings were proper. If "they" rejoiced in this manner, it was not improper for "him" to show similar joy, and especially to seek their conversion and salvation. If they rejoice also, it shows how desirable is the repentance of a sinner.

They know of how much value is an immortal soul. They see what is meant by eternal death; and they do not feel "too much," or have "too much anxiety" about the soul that can never die. Oh that people saw it as "they" see it! and oh that they would make an effort, such as angels see to be proper, to save their own souls and the souls of others from eternal death! -- Clarke's Commentary on the Bible

There are some, and their opinion need not be hastily rejected, who imagine that by the ninety and nine just persons, our Lord means the angels - that they are in proportion to men, as ninety-nine are to one, and that the Lord takes more pleasure in the return and salvation of one sinner, than in the uninterrupted obedience of ninety-nine holy angels; and that it was through his superior love to fallen man that he took upon him his nature, and not the nature of angels.

I have met with the following weak objection to this: viz. "The text says just persons; now, angels are not persons, therefore angels cannot be meant."

This is extremely foolish; there may be the person of an angel, as well as of a man; we allow persons even in the Godhead; besides, the original word, δικαιοις, means simply just ones, and may be, with as much propriety, applied to angels as to men.

After all, our Lord may refer to the Essenes, a sect among the Jews, in the time of our Lord, who were strictly and conscientiously moral; living at the utmost distance from both the hypocrisy and pollutions of their countrymen. These, when compared with the great mass of the Jews, needed no repentance. The reader may take his choice of these interpretations, or make a better for himself. I have seen other methods of explaining these words; but they have appeared to me either too absurd or too improbable to merit particular notice. -- Clarke