This fragment of a verse come from a psalm that is magnifying what God does, and how he has protected Israel. And in the midst of this praise is this simple admonition. To be still. And to know that the Lord (YHWH) is God.
This psalm of David is a prayer for God’s presence and leading. It is the cry of a heart that yearns to know more and more of God. A heart that wants to know and follow his truth. A heart whose hope was not in power or strength of arms, but in God.
God’s instruction to Joshua cannot be over-stressed. In order to have a successful and prosperous spiritual journey, I need to invest quality time in the Bible. Read it. Meditate on what it says. Listen to the Holy Spirit’s instruction. And obey its teachings. Then you will be successful.