Iron Sharpening Iron

I think all Christians know Pro. 27:17, "As iron sharpens iron, so one man sharpens another."  It seems that verse is applied almost exclusively to relationships between Christians.  However, in spending time with someone who doesn't know Christ, I have been sharpened immensely.  My thinking has been greatly challenged as I study to be prepared in case this or that specific issue comes up.  Don't let yourself be fooled into thinking God only uses fellow Christians to lead us on to spiritual maturity.  And don't forget to thank Him for your non-Christian friends who challenge and stretch you, and also thank them while you're at it.