Lift your voice as a trumpet for the Day of the Lord

Numbers 29:1-6 (KJV)
And in the seventh month, on the first day of the month, ye shall have an holy convocation; ye shall do no servile work: it is a day of blowing the trumpets unto you. [2] And ye shall offer a burnt offering for a sweet savour unto the Lord ; one young bullock, one ram, and seven lambs of the first year without blemish: [3] And their meat offering shall be of flour mingled with oil, three tenth deals for a bullock, and two tenth deals for a ram, [4] And one tenth deal for one lamb, throughout the seven lambs: [5] And one kid of the goats for a sin offering, to make an atonement for you: [6] Beside the burnt offering of the month, and his meat offering, and the daily burnt offering, and his meat offering, and their drink offerings, according unto their manner, for a sweet savour, a sacrifice made by fire unto the Lord .

It is a day of blowing trumpets to you. What does this day signify? Firstly, it was a reminder and a proclamation to the Israelites of the Law of God given on mount Sinai:
Exodus 19:16-19 (KJV)
And it came to pass on the third day in the morning, that there were thunders and lightnings, and a thick cloud upon the mount, and the voice of the trumpet exceeding loud; so that all the people that was in the camp trembled. [17] And Moses brought forth the people out of the camp to meet with God; and they stood at the nether part of the mount. [18] And mount Sinai was altogether on a smoke, because the Lord descended upon it in fire: and the smoke thereof ascended as the smoke of a furnace, and the whole mount quaked greatly. [19] And when the voice of the trumpet sounded long, and waxed louder and louder, Moses spake, and God answered him by a voice.
Trumpet of God called Israel out of the camp to meet with God to the edge of the mount, from which God proclaimed His ten commandments. So then, as the trumpets were blown on this day, Israel were to remind themselves of Sinai and the moral law of God. They were to teach themselves again the ten commandments of love, and see where they have failed.

This seems suitable, as the day of atonement came on the 10th day of the same month. For ten days they were to think over the ten commandments, being convicted and threatened and burdened by it, but on the day of atonement find relief. The trumpet proclamation of the law prepares the sinner's heart for the gospel. A man must come to Sinai and its threatenings, before he can truly understand the significance of what Christ has done. A man must be cursed by the law, before he can be blessed through Christ. A man must realize his deadness in sin, before realizing that life can come to him through the death of God's Son. A man must be totally condemned, before he can see the value of justification by faith alone. There must be a revelation of sin by the light of the Spirit, before a soul seeks after the healing flow of Christ's blood.
Trumpet in the scriptures is the sound of alarm, sound of warning against transgressors of coming judgment and of war. It is fitting then God sounded forth His trumpet in proclamation of the Law, since the Law proclaimed God's hostility against man. God is against sinners, since they are against His Law of Love. Sinners have failed to love God and people and therefore there is coming judgment upon them. Trumpet of warning is to be blown against them:
Isaiah 58:1 (ESV)
"Cry aloud; do not hold back; lift up your voice like a trumpet; declare to my people their transgression, to the house of Jacob their sins.
Jeremiah 6:17 (ESV)
I set watchmen over you, saying, ''Pay attention to the sound of the trumpet!''But they said, ''We will not pay attention.''
Ezekiel 33:4 (ESV)
then if anyone who hears the sound of the trumpet does not take warning, and the sword comes and takes him away, his blood shall be upon his own head.

Listen to the voice of the prophets, which are like trumpets of the alarm of war, the alarm of the wrath of God that is to come upon the earth. We do well do be alarmed by the sound the the trumpets that we hear from our preachers in the pulpits. The natural disasters and the tolerance of wicked sins that we see around the earth today should be an alarm of trumpet to us. God is constantly warning mankind of the dangers of sin by His Holy Spirit today through the instruments of men. For hear the trumpet sound of the Holy Spirit:
John 16:8-11 (ESV)
And when he comes, he will convict the world concerning sin and righteousness and judgment: [9] concerning sin, because they do not believe in me; [10] concerning righteousness, because I go to the Father, and you will see me no longer; [11] concerning judgment, because the ruler of this world is judged.

The preaching of the Gospel itself then can also be referred to this sounding of the trumpet. The trumpet sounded from Sinai, now sounds even more terrifying sounds from the hill of Calvary. It is not the law that sounds forth from there, but the news of what God has done. While it is good news, happy news, it is also the most terrifying news. It is the final warning against sinners. The trumpet call from the hill of Golgotha proclaims this: "If the Son of God had to die in this way, crushed under the feet of God, to save a people, will God spare punishment from those who do not repent and put their trust in the only Saviour? No. Sinners must die, cursed, like as Christ as died". And the worse thing that the trumpet of Calvary proclaims is this: "Man has treated the Son of God with such contempt, who has done nothing but good to man in return. Man has killed God who visited earth in human flesh. Though man has done this most horrible crime, if they repent and put their trust in the Risen Son, they will not perish. However, if they still do not believe, expect the wrath of the Father to fall upon you taking vengeance for His Son!!" This call is much more frightening than the threatenings of Sinai, because Law was about justice, but to ignore the trumpet of Calvary is to ignore God's final plea of love and grace. Reader, if you have never put your trust in Christ, do it today, for God will take vengeance upon the earth for its sins, especially those who reject His Son, His final offer for you!

The trumpet also signifies the appointing of the king in the scriptures:
1 Kings 1:34 (ESV)
And let Zadok the priest and Nathan the prophet there anoint him king over Israel. Then blow the trumpet and say, ''Long live King Solomon!''
2 Kings 9:13 (ESV)
Then in haste every man of them took his garment and put it under him on the bare steps, and they blew the trumpet and proclaimed, "Jehu is king."
Through this feast, Israel were perhaps to remind himself that God is the King over them. We are also to proclaim, lifting our voices that Jesus is the King of the world that God has set for Himself. Jesus is our King and He is our law giver. We are to live in submission and obedience to His will. We are to celebrate that He is King over us, that He has freed us from the dominion of sin and of the world. We are to proclaim that there is a new King that has been anointed, and that the Kingdom of God is come upon the kingdoms of men. As Jesus said:
Matthew 21:44 (ESV)
And the one who falls on this stone will be broken to pieces; and when it falls on anyone, it will crush him."
This stone is Jesus Christ. Him we proclaim, that He not only died and rose again, but that He will come back as a Rock of stumblingblock and a Rock of offense upon the earth. Jesus is not the king of this world, as He said, but He is the King of the coming Kingdom that is already here, and is ready to invade the world in a short time.

What are we to do as Christians? We are to proclaim the word of God as watchmen. We are to proclaim that God is against the world for their sins, and we are to show them their sins. We are to proclaim repentance. Then, we are to proclaim the Good News of God, of the goodwill that God has done for sinners. We are also to proclaim that Jesus Christ is Lord of all the earth, and that He shall come and judge the world of its sins. For the Day comes in which God shall take vengeance upon all the earth:
Joel 2:1-2 (ESV)
Blow a trumpet in Zion; sound an alarm on my holy mountain!Let all the inhabitants of the land tremble, for the day of the LORD is coming; it is near, [2] a day of darkness and gloom, a day of clouds and thick darkness!Like blackness there is spread upon the mountains a great and powerful people;their like has never been before, nor will be again after them through the years of all generations.
Let us have our trumpet to sound ready at all times, and warn the inhabitants of the world of the Day of the Lord. Who shall abide in the Day of His coming? It shall be like a refiner's fire. Who shall stand and not be ashamed at His coming? Those who trust in the righteousness of Christ and are walking in the love of the Father. All shall give an account of their lives, and by their words they shall be damned, and by their words they shall be justified. Those who trusted in themselves, shall be blown away like chaff in the wind. On the Day, God as He revealed Himself upon Sinai shall be upon every man like a consuming fire. Who shall be saved? Only those whose names are written in the book of life of the lamb slain from the foundation of the world. Knowing the terror of the Lord, let us warn every man, lifting up our voices trumpets. Let us not fear man, but God who will soon judge the world:
Matthew 10:27-28 (KJV)
What I tell you in darkness, that speak ye in light: and what ye hear in the ear, that preach ye upon the housetops. [28] And fear not them which kill the body, but are not able to kill the soul: but rather fear him which is able to destroy both soul and body in hell.