1 Corinthians 15:52

in a split second, as quickly as the twinkle of an eye, when the last trumpet blows. For the trumpet will blow and dead people [i.e., believers] will be raised up, never to decay again, and [the living] will be changed [i.e., physically and spiritually].

1 Thessalonians 4:16

For the Lord Himself [i.e., Jesus] will come down from heaven with a commanding shout [Note: This probably refers to Jesus' voice. See John 5:25, 28], [and] with the archangel's voice [i.e., Michael. See Jude 9] and with the sound of God's trumpet; [at this] the dead in [fellowship with] Christ will rise [from the dead] first.

Hebrews 12:20

For those people could not stand [hearing] the command [Ex. 19:12f], "If even an animal touches the mountain, it must be stoned [to death]."

Treasury of Scripture Knowledge

Summary

There shall not an hand touch it, but he shall surely be stoned, or shot through; whether it be beast or man, it shall not live: when the trumpet soundeth long, they shall come up to the mount.

Bible References

When the trumpet

1 Corinthians 15:52
in a split second, as quickly as the twinkle of an eye, when the last trumpet blows. For the trumpet will blow and dead people [i.e., believers] will be raised up, never to decay again, and [the living] will be changed [i.e., physically and spiritually].
1 Thessalonians 4:16
For the Lord Himself [i.e., Jesus] will come down from heaven with a commanding shout [Note: This probably refers to Jesus' voice. See John 5:25, 28], [and] with the archangel's voice [i.e., Michael. See Jude 9] and with the sound of God's trumpet; [at this] the dead in [fellowship with] Christ will rise [from the dead] first.