The “vine” and “fig tree” are both native to Israel. They flourish into luxuriant, natural arbors under which people can sit and enjoy fellowship while being shaded from the heat of the day. Both were used symbolically to represent the basic covenant between God and Israel in all its potential fruitfulness.
But they shall sit every man under his vine and under his fig tree; and none shall make them afraid: for the mouth of the Lord of hosts hath spoken it.
It is usual in eastern countries to sit under vines and fig trees to read, meditate, pray or converse together like a fellowship.
Fear is the opposite of faith. The people this is speaking of are the faithful. They will not know fear, because they have faith in Jesus Christ the King of peace. When perfect peace reigns, there will be prosperity.
Second Coming of Christ
When Jesus returns there will be no more want. There is sufficient food in the world to feed everyone. All we lack is the will as a fellowship. When Jesus returns no one will lack for needs. No more war. No more poverty.
There shall be glorious church of God in the world, in the last days of the Messiah. Christ himself will build it upon a rock. The Gentiles worshiped their idol gods; but in the period spoken of the people will cleave to the Lord with full purpose of heart and delight in doing his will. The reign of Christ shall continue till succeeded by the everlasting kingdom of heaven.
A disposition to mutual peace and love shall be the happy effect of the setting up of the kingdom of the Messiah. As far as the gospel prevails it makes men peaceable, for such is the wisdom from above; it is gentle and easy to be entreated and if nations were but leavened by it, there would be universal peace.