Mosiah 27:11 - 27:15

Mosiah 27:11 And as I said unto you, as they were going about rebelling against God, behold, the angel of the Lord appeared unto them; and he descended as it were in a cloud; and he spake as it were with a voice of thunder, which caused the earth to shake upon which they stood;

Now the Lord directly intervenes in this situation. He sends an angel. The angel descends in a cloud and when he spoke the ground shock and was as loud as thunder.
[It must have been a freighting scene for these boys to see an angel appear out of a cloud with power and glory surrounding him. And to have the ground shake under them as the angel spoke must have let them know just how weak and powerless they were against the power of the angel. That really got their full and undivided attention.]

Mosiah 27:12 And so great was their astonishment, that they fell to the earth, and understood not the words which he spake unto them.

In fact it scared them so bad that they all fell to the ground and their amazement was so profound that they failed to understand the words of the angel.

Mosiah 27:13 Nevertheless he cried again, saying: Alma, arise and stand forth, for why persecutest thou the church of God? For the Lord hath said: This is my church, and I will establish it; and nothing shall overthrow it, save it is the transgression of my people.

The angel tells Alma to stand up and asks why is he giving the Church such a hard time? The angel quoted the Lord saying that only wickedness by the people themselves will destroy it not the efforts of a few malcontents.

Mosiah 27:14 And again, the angel said: Behold, the Lord hath heard the prayers of his people, and also the prayers of his servant, Alma, who is thy father; for he has prayed with much faith concerning thee that thou mightest be brought to the knowledge of the truth; therefore, for this purpose have I come to convince thee of the power and authority of God, that the prayers of his servants might be answered according to their faith.

The reason for his appearance is to convinced them of the stupidity of their efforts to destroy the Church. His father had prayed with great earnestness for his son to be brought to understand the great evil he was committing and to be brought to his senses again.

Mosiah 27:15 And now behold, can ye dispute the power of God? For behold, doth not my voice shake the earth? And can ye not also behold me before you? And I am sent from God.

The angel now asks Alma Jr. if he can dispute the power that God has? God has so much power that He can make the ground shake when he speaks. And this angel has come from God’s presence to convince him of his wickedness.