I'm preaching, on May 17, at Redeemer, on Galatians 6:4-6.
You can listen to my message here.
Here are a few resources to dig deeper.
Craig Keener article - Once-Saved-Always-Saved? Maybe not - Bible Backgrounds
Craig Keener two minute video - Different Views of Hebrews 6:4-6
John Piper - 7 minute video - Can Christians Lose Their Salvation?
Ben Witherington - John Piippo: Ben Witherington on Eternal Security
William Lane Craig - 20 minute video - Can We Lose Salvation? | Doctrine of Salvation pt 21: Assessment of Perseverance || Defenders LIVE!
Al Mohler - 7 minute video - (1) Video | Facebook
Greg Boyd - Free For All Q&A - Can I lose my salvation?