To stand up for something or someone is to take a stand for it. To stand up for the Lord means we have the courage to swim upstream, and to say and do things that are unpopular in our world. It is to truly rise up for the Lord and start living a holy life. as we're taught in Psalm 1. It is easy to swim downstream, to go with the flow, to live as the crowd does. It takes a real man or woman to stand and walk with God. It also make God's heart glad.
" Oh, the joys of those who do not follow the advice of the wicked, or stand around with sinners, or join in with mockers."
Psalm 1:1 (NLT)