Psalm 141:3 Set a guard, O Lord, over my mouth; keep watch over the door of my lips!
Numerous other verses in the Bible also talk about the power of the tongue to inflict life or death upon those around us. The tongue wields such huge power - we can use it to build people up, or we can use it to tear them down. Oh, that we would hold our tongue, that we would think before speaking foolishly. As Thumper said in the movie Bambi - if you can't say something nice, don't say nothing at all. Advice we'd be wise to heed.
Psalm 141:4 Let not my heart be drawn to what is evil, to take part in wicked deeds with men who are evildoers; let me not eat of their delicacies.
As my Life Application Bible says.... David asked God to guard his heart. Evil acts begin with evil desires. It isn't enough to ask God to keep you away from temptation, make you stronger, or change your circumstances. You must ask him to change you on the inside at the level of your desires.
2 Corinthians 12 deals a deathblow to the prosperity gospel. I don't think anyone would have the audacity to suggest they had more faith than the apostle Paul, and God did not heal Him, even though Paul prayed for healing and even though Paul believed God could heal Him. We know that God is capable of healing anyone, but we also know that sometimes He choose not to, or chooses to heal them eternally instead. We don't know why other than that God always does things for His glory.
It reminds me of when our nephew was deathly ill and the doctors had given zero hope of a recovery. We knew it would only be a miracle by God's grace that would save Him and we prayed desperately for this miracle. We knew God could heal Him, but we didn't know if He would. We are so thankful that God chose to heal Him and that we were able to give Him the glory for that miracle. But we also know that if God chose not to heal Him it wouldn't be saying anything about the strength of our faith or lack thereof.
Tomorrow's Bible In a Year Passage passage: Psalms 143-145; 2 Corinthians 13