Out of the treasure of your heart
"A good man out of the good treasure of his heart bringeth forth that which is good; and an evil man out of the evil treasure of his heart bringeth forth that which is evil: for of the abundance of the heart his mouth speaketh." (Luke 6:45 KJV)
"Auto Responder" Mechanism
I spend a lot of time finding and applying God's promises to my life! Because of this habit, the promises are always on my mind and often just roll off my tongue instantly and without thinking while I'm in a conversation with just about anyone. This 'auto responder mechanism' happens because "out of the abundance of a man's heart, so he speaks".
It happens for everyone
This auto-process actually happens for everyone, not just for me! But the subject matter varies. My sports minded friends can roll off amazing sports facts and statistics instantly because that is what they love, think about, concentrate on, are passionate about, and have filled their minds with, and so it just instantly comes out of their mouths effortlessly. I have some friends who are always "talking politics" and other friends with other interests they care a lot about, and so that's what they talk constantly about. Whatever is foremost on their minds gets talked about with enthusiasm and often passionately. Some of these friends are amazed that I can quote so much scripture without looking at the Bible.
How I Do It
They sometimes ask me how I am able to do it. Truthfully, I do not work at memorizing Bible verses, I just spend a lot of time reading the Bible, looking up things and thinking about what I have read. And, because that is what I am focused on, it comes out easily in conversation. Truthfully, I am amazed at others who can remember so much sports stuff. But again, it's a matter of focus. If you want to have the powerful Word of God at work in your life and have it pour out your mouth easily, you have to make the Word of God your "treasure". Incidentally, a few years ago I had a booth at a business trade show and spent several days talking business to many prospects who stopped by to talk about my products. When the show ended, and I was packing up, a man from the booth next to mine came over to speak with me. He reached out to shake my hand and got tears in his eyes as he spoke to me. He said, "Mike, it was a pleasure being next to you and it was such a blessing and inspiration to me. I am a brand new Christian and I just marveled over and over how easily you quoted scripture to people and shared your faith so easily with people!" I thanked him for his kind words, but truthfully, I couldn't remember having spoken to a single person at that trade show about God! But, that's what happens when the Word of God becomes a part of your normal speech. It just happens without you really noticing. Make God's Word your focus and eventually you will "have the mind of Christ" and His Word will come out of your mouth from "the abundance of your heart!"