Isaiah 6

"Then one of the seraphim flew to me, having in his hand a live coal which he had taken with the tongs from the altar.  And he touched my mouth with it, and said: “Behold, this has touched your lips; Your iniquity is taken away, And your sin purged.”  vv.6-7

Read chapter 6.

What would happen to you if a live coal touched your lips?  They'd burn of course.  This did in fact happen to Isaiah and was not a metaphor, yet one we can apply to us.  As the seraphim took the hot coal from the altar, which showed the sin and need for purification, and touched Isaiah's lips taking his sin away, so Christ's death took our sins away by not even a touch of our bodies yet our need to be made pure.  The Holy Spirit in us makes us clean and purged from sin.  "this is a sign that the guilt of thy sin is removed by pardoning mercy, and thy corrupt disposition and inclination to sin, by renewing grace; and, therefore, nothing can hinder thee from being accepted of God, as a worshipper, in concert with the holy angels; or from being employed for God, as a messenger to the children of men. Those only, who are thus purged from an evil conscience, are prepared to serve the living God,"  (Benson Commentary).  As we continue to read in this chapter we see that once Isaiah's made clean he has this God given desire to serve.  When have you been shown grace or mercy that has then resulted in your desire to serve God through others or another area of life?