We make a phone call and forget to hang up when it is over; we may then hear a conversation on the other end that we wish we had not heard.  Grumbling is that way.  “Do not grumble against one another, brothers, so that you may not be judged; behold, the Judge is standing at the door” (James 5:9 ESV).  If I know that my grumbling is heard by the Judge of all, it will change what I say and how I say it.  The Lord is always the witness to our conversations and those under-our-breath murmurings.  What He is overhearing is more than words; He hears our impatience, our lack of faith, and un-Christlike expressions.  Think about it children!