Mark 13:7

but when ye shall hear the talk of wars, and the noise of wars, be not alarm'd; for that must happen; but the end is not yet.

Matthew 18:7

wo unto the world, because of such scandals: tho' it cannot be, but that such occasions of relapsing should happen: yet wo to that man by whom the scandal cometh.

Matthew 24:6-7

ye shall hear likewise of wars, and rumours of wars: take care not to be disturb'd: for these things must happen, but the end of the Jewish age is not yet.

Luke 21:9-11

And when ye shall hear of wars, and seditions, be not alarm'd. for these must first happen: but the end will not be so soon.

John 14:1

Let not your heart be troubled: you trust in God, trust also in me.

John 14:27

I bid you farewell! I give you my last farewell; but I do not give it out of common formality: don't be concern'd for me, or apprehensive for your selves.

Acts 17:3

explaining them, and setting it to view, that the Messiah was to suffer and rise again from the dead: and that Jesus, whom he denounc'd to them, was that very Messiah.

Treasury of Scripture Knowledge

Summary

And when ye shall hear of wars and rumours of wars, be ye not troubled: for such things must needs be; but the end shall not be yet.

Bible References

When

Matthew 24:6
ye shall hear likewise of wars, and rumours of wars: take care not to be disturb'd: for these things must happen, but the end of the Jewish age is not yet.
Luke 21:9
And when ye shall hear of wars, and seditions, be not alarm'd. for these must first happen: but the end will not be so soon.
John 14:1
Let not your heart be troubled: you trust in God, trust also in me.

Must

Matthew 18:7
wo unto the world, because of such scandals: tho' it cannot be, but that such occasions of relapsing should happen: yet wo to that man by whom the scandal cometh.
Acts 17:3
explaining them, and setting it to view, that the Messiah was to suffer and rise again from the dead: and that Jesus, whom he denounc'd to them, was that very Messiah.