Although I probably have 50 commentary sets in my digital library, I use the Ancient Christian Commentary and The Preacher's Outline and Sermon Bible (POSB) all the time as my two main go to references. Both, especially the POSB are indispensable to me. By using the Ancient Christian Commentary I can see how much denominations has changed in their thinking since Christ established "The Church", and prayed for us "all" to be one. We suffer now as Paul did with the Corinthian Church; they were broken up into factions ; I follow Apollos, I follow Silas, I follow Peter, and some followed Paul. There is only one church that the Lord died for and Paul tells us that. Follow Jesus, and not men!