How do we understand St. Matthew and St. James in their writings as they talk against swearing and oaths ("swear not at all")? On a surface level, it appears all swearing/oaths are not to be practiced by God's people. If I'm not mistaken, I believe the first 300 years of the church held to this as necessary to be obeyed for all Christians. Thanks.
There is no absolute prohibition in the Bible regarding taking oaths. In Matthew 5:33-37 and James 5:12, we find instructions not to swear—using God as our witness to assure people we are telling the truth—needlessly and thoughtlessly. When taking an oath is necessary, we can comply. Jesus’ own example in Matthew 26:63-64 illustrates that.
I am not sure which sources you might be referencing for your thoughts on the early Christian Church’s views toward taking oaths. In general, most Christians have held to the view stated above.