"Earlier in chapter fourteen we met three angels, each bearing a message to the inhabitants of the earth-realm. Another angel now appears, the first of a second series of three, and styled “another,” not by comparison with Him who sits upon the white cloud, but by comparison with the three angels previously spoken of in the sixth, eighth, and ninth verses of the chapter. He is called an “angel” with reference to his mission, not with reference to his nature. He is not a shining personage with wings flying through the atmosphere. The symbol stands for the issuing forth of the word of God. Each messenger represents the coming forth of a powerful proclamation of the Spirit! This angel, or messenger, is said to come out from the temple — that is, out of the naos, out of the innermost shrine of the temple, the most holy place; out from the deepest depths of the divine spirit, and out from the manifest presence of the Lord in the temple of His body — and this truth is important, for it shows that this is a message, a word, a revelation, a proclamation coming forth right out of the heart of God in His called and chosen elect. This word is as a prayer, as a prophecy, as a mighty declaration by the Spirit unto the Lord Jesus Himself, just as one might speak by the Spirit on behalf of a sick man and command, “Lord Jesus, heal him!” Only this command to the Lord is thus: “Send forth Thy sickle and reap… for the harvest of the earth is ripe!” Is not this the very fulfillment of the instructions the Lord Himself has given us — “The harvest truly is great, but the laborers are few: PRAY ye therefore the Lord of the harvest, that HE would send forth laborers into His harvest” (Lk. 10:2). "

Much more in the link:

https://www.godfire.net/eby/rev171.html