I can relate to this question because it happened to me when I least expected it.
I was about to begin my Bible study when a newcomer entered the room. I did not recognize this woman, and she did not appear to arrive with anyone else. But I was glad to have someone new join my group, and I greeted her with a friendly smile and welcome.
As I taught from God's Word, I made eye contact with each woman in the room. I did not notice any unusual facial expressions or concerns coming from her over what I was saying. But then again—looks can be deceiving.
When the Bible study ended, and everyone packed up their belongings to leave, I walked up to this woman and thanked her for coming. She was very polite and seemed appreciative of my gratitude. Then she said something about God's Word related to my message, which I agreed with wholeheartedly.
I cannot recall her next theological statement about salvation, but my brain suddenly thought, "Wait, what?"
It took me a few seconds to brace myself for what I knew was happening. But I never expected a theological challenge to arise at my Bible study. I was not mentally prepared for a debate, so I quietly took a deep breath before opposing what she said. I hoped my words would disarm her argument, but my efforts failed.
Over the next 15-20 minutes, she tried to prove salvation was earned by obeying the Torah. I refuted her statements with the truth every time she made a false claim. But when she started quoting verses out of context, I knew I needed to arm myself with "chapter and verse" to combat her heretical doctrine.
I quickly grabbed my cellphone and accessed ScriptureSubjects.net.
I immediately went to the "Salvation: Gift by Faith Alone" Scripture references section and quoted many verses that contradicted her erroneous theology. But she refused to accept them.
Although I did my best to present her with the gospel truth, she rendered me a heretic and false teacher. Eventually, I ended the discussion because she was unwilling to budge on her position, and I refused to compromise the truth. Not surprisingly, I never saw or heard from her again.
I wish I could say I enjoy unexpected, in-person theological debates, but they always make me nervous. Nonetheless, Jesus has used them to fortify my resolve to speak and present the truth even when it is rejected. He has also utilized these encounters to sharpen my knowledge of biblical truth and prepare me for future theological arguments and tactics that will undoubtedly present themselves.
Therefore, when someone challenges your beliefs and the truths of God's Word, I encourage you to let the Bible speak for itself. This approach will require you to become familiar with essential doctrines and the verses that authenticate them, so you can "present your case" adequately.
This is the reason I created Scripturesubjects.net—to help you contend for the truth and defend your faith. If you have not explored the wealth of information it offers, including the multiple lists of Bible verses arranged topically, I urge you to acquaint yourself with the website and take advantage of its free commentaries, Scripture references, and other resources.
Finally, if you find yourself contending for the truth but the other person repeatedly rejects your words, be discerning about when to pull the plug on the conversation. Discussions about spiritual matters can turn ugly very quickly, so listen to the Holy Spirit's voice and end it while it is still cordial. Then pray for Jesus to open that person's eyes to the truth and move forward.
I hope this information helps you continue to fight the good fight of faith!