Acts 16:6-10
(6) Now when they had gone throughout Phrygia and the region of Galatia, and were forbidden of the Holy Ghost to preach the word in Asia,
(7) After they were come to Mysia, they assayed to go into Bithynia: but the Spirit suffered them not.
(8) And they passing by Mysia came down to Troas.
(9) And a vision appeared to Paul in the night; There stood a man of Macedonia, and prayed him, saying, Come over into Macedonia, and help us.
(10) And after he had seen the vision, immediately we endeavoured to go into Macedonia, assuredly gathering that the Lord had called us for to preach the gospel unto them.

Numbers 10:1-3 & 10
(1) And the LORD spake unto Moses, saying,
(2) Make thee two trumpets of silver; of a whole piece shalt thou make them: that thou mayest use them for the calling of the assembly, and for the journeying of the camps.
(3) And when they shall blow with them, all the assembly shall assemble themselves to thee at the door of the tabernacle of the congregation.
(10) Also in the day of your gladness, and in your solemn days, and in the beginnings of your months, ye shall blow with the trumpets over your burnt offerings, and over the sacrifices of your peace offerings; that they may be to you for a memorial before your God: I am the LORD your God.