Mount Zion is specifically referred to a total of 40 times in the Psalms. Originally known as the fortress of Jerusalem, it was a little lower than the city mount itself and when David conquered it, it became his residence. As time went on however, it became a title for the temple mount itself and for the entire city of Jerusalem. Ultimately, it is the home of God.
Psalm 125 speaks of Jerusalem as having lost its independence: “wicked” men now (during the time of the Psalm) rule over her. But the writer is convinced that this will not persist. God will not allow his domain to be sullied by those not His people.
Which brings up this point: If God is God and Zion is His city, why is it being occupied by God’s enemies?
The Psalmist does not answer this question – or even, apparently, think about it. It is important that God act so that the righteous might not be influenced to do evil.
I think this is a good motivation for us to use as well. Admittedly, it’s tough sometimes to be faithful when evil is so prevalent and appears to be winning. We pray for God to act before we are led into temptation and we ask him to deliver us from the conflicting thought that trouble us. Instead, we seek the peace He can give.