But they shall sit every man under his vine and under his fig-tree; and none shall make them afraid; for the mouth of YHWH Tzava'ot has spoken it.
The most obvious meaning of this passage from the context is there is no one to make Israel afraid any longer. He is dwelling in safety and security. Each man is dwelling under his own tree and under his own vine. However, while this is readily apparent from the context, it is far from being the end of what dwelling under one's one tree and vine means. This passage speaks on many levels as to how a Torah society is supposed to function.
Both the vine and the fig tree bear fruit which is good for food. Thus, one of the meanings here is that each man is producing his own food. This is one of the things that gives him reason to be secure; he does not need to depend upon others in order to be able to feed and clothe his family. We include the ability to clothe himself as well as feeding himself because of what man originally did in the garden.
Likewise, each man sitting under his own tree, specifically, his own fig tree, suggests the sin of Adam and Chavah in Gan Eden.
B'reshit (Genesis) 3:7
And the eyes of them both were opened, and they knew that they were naked; and they sewed fig-leaves together, and made themselves aprons.
As a result of rebelling against the Voice of YHWH, man hid his nakedness by putting on fig leaves. We are not suggesting man is going to return to that state. However, what it does seem to suggest concerning man's future state by one sitting under his own fig tree, indicates each person will be fully aware of his own shortcomings and sin. He will not be looking at the other man's sin and pointing his finger at his neighbor any longer. He finally fully realizes he is not worthy of being in the presence of YHWH.
Yonah (Jonah) 4:6-7
6 And YHWH Elohim prepared a gourd, and made it to come up over Yonah, that it might be a shade over his head, to deliver him from his evil case. So Yonah was exceeding glad because of the gourd.
7 But Elohim prepared a worm when the morning rose the next day, and it smote the gourd, that it withered.
Both the vine and tree suggest other passages of Scripture. Each man sitting under his own vine suggests the account of Yonah. The vine of Yonah suggests both repentance and mercy. Not only is each man to repent and return to YHWH, but each man is also to show his neighbor the mercy he received from YHWH. If he does not, then his vine shall wilt.
Furthermore, each person sitting under his own vine and tree also suggests each person is minding his own business. He is not being a busybody nor attempting to dictate to his neighbor how his neighbor should live his life. Rather, each person is sitting under his own tree at peace with himself as well as at peace with his neighbors and with his brothers. This is what a true Torah society should look like.