In the strength of the Lord: We need His strength because the devil is stronger than we are – but he’s not stronger than the Lord.
The armour provided by the Lord (Ephesians 6:13-17): All of it is defensive except “the sword of the Spirit” (God’s Word).
In Ephesians 6:18, there’s a call to prayer. It’s general – “every prayer … at all times with all perseverance for all the saints.”
In Ephesians 6:19-20, there’s a call for specific prayer for those who are called to preach the Gospel. Paul is asking for prayer for himself. The Holy Spirit brings to us these words from the past. He brings them to us with power – so that we may know that God has given us everything that we need for living to his praise and glory.