Then said he, Knowest thou wherefore I come unto thee? and now will I return to fight with the prince of Persia: and when I am gone forth, lo, the {p} prince of Grecia shall come.

(p) Meaning that he would not only himself bridle the rage of Cambyses, but also the other kings of Persia by Alexander the King of Macedonia.

Wesley's Notes

10:20 To fight - To oppose his mischievous designs.

Jamieson-Fausset-Brown Bible Commentary

20. Knowest thou wherefore-The angel asks, after Daniel had recovered from his fright, whether he has understood what was revealed (Da 10:13). On Daniel, by his silence, intimating that he did understand, the angel declares he will return to renew the fight with the evil angel, the prince of Persia. This points to new difficulties to the Jews' restoration which would arise in the Persian court, but which would be counteracted by God, through the ministry of angels.

prince of Grecia shall come-Alexander the Great, who conquered Persia, and favored the Jews [Calvin]. Rather, as the prince of Persia is an angel, representing the hostile world power, so the prince of Grecia is a fresh angelic adversary, representing Greece. When I am gone forth from conquering the Persian foe, a fresh one starts up, namely, the world power that succeeds Persia, Greece; Antiochus Epiphanes, and his antitype Antichrist, but him, too, with the help of Michael, Israel's champion, I shall overcome [Gejer].

Matthew Henry's Concise Commentary

10:10-21 Whenever we enter into communion with God, it becomes us to have a due sense of the infinite distance between us and the holy God. How shall we, that are dust and ashes, speak to the Lord of glory? Nothing is more likely, nothing more effectual to revive the drooping spirits of the saints, than to be assured of God's love to them. From the very first day we begin to look toward God in a way of duty, he is ready to meet us in the way of mercy. Thus ready is God to hear prayer. When the angel had told the prophet of the things to come, he was to return, and oppose the decrees of the Persian kings against the Jews. The angels are employed as God's ministering servants, Heb 1:14. Though much was done against the Jews by the kings of Persia, God permitting it, much more mischief would have been done if God had not prevented it. He would now more fully show what were God's purposes, of which the prophecies form an outline; and we are concerned to study what is written in these Scriptures of truth, for they belong to our everlasting peace. While Satan and his angels, and evil counsellors, excite princes to mischief against the church, we may rejoice that Christ our Prince, and all his mighty angels, act against our enemies; but we ought not to expect many to favour us in this evil world. Yet the whole counsel of God shall be established; and let each one pray, Lord Jesus, be our righteousness now, and thou wilt be our everlasting confidence, through life, in death, at the day of judgment, and for evermore.