Have you noticed that the best source of comfort is someone who has struggled with pain, sorrow, or loss? That is one reason why God offers His followers the gift of comfort, so that we can, in turn, give it to others. Yes, God sometimes allows tragedy to enter our lives, but He never intends for us to go through difficult times alone. Once we have — by God’s grace — gone through a dark time, God calls us to offer comfort to the hurting people He puts in our path. Often that comfort is our mere presence, not “right” words.
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Our willingness to share the kind of comfort we have received reflects both our knowledge of our good God and our faith in Him.

And whether we are receiving or offering comfort, we can rely on the greatest Comforter of all, the Holy Spirit. Given to us by God, the Spirit is continually with us, willing to guide and empower us as we come alongside hurting people. Yes, our Redeemer-God is at work when He uses the comforted to comfort others!

Blessed be the God and Father of our Lord Jesus Christ, the Father of mercies and God of all comfort, who comforts us in all our tribulation, that we may be able to comfort those who are in any trouble, with the comfort with which we ourselves are comforted by God. For as the sufferings of Christ abound in us, so our consolation also abounds through Christ. Now if we are afflicted, it is for your consolation and salvation, which is effective for enduring the same sufferings which we also suffer. Or if we are comforted, it is for your consolation and salvation. And our hope for you is steadfast, because we know that as you are partakers of the sufferings, so also you will partake of the consolation. — 2 Corinthians 1:3–7

From http://www.faithgateway.com