'Understand' in the Bible

Behold, I will wave my hand over them and they shall become plunder for their own slaves. Then you shall know (recognize, understand fully) that the Lord of hosts has sent Me.

Many nations shall join themselves to the Lord in that day and shall be My people. And I will dwell in your midst, and you shall know (recognize, understand fully) that the Lord of hosts has sent Me to you.

“The hands of Zerubbabel have laid the foundations of this house, and his hands will finish it. Then you will know (recognize, understand fully) that the Lord of hosts has sent me [as His messenger] to you.

And those who are far away will come and [help] build the temple of the Lord.” Then you shall know [without any doubt] that the Lord of hosts sent me (Zechariah) to you. And it will come about if you will diligently obey the [voice of the] Lord your God.