St. Paul counsels the Colossians, "And let the peace of God rule in your hearts, to the which also ye are called in one body; and be ye thankful." In today's Gospel, ten lepers stand afar off (as lepers, they are outcasts of society and dare not approach too closely) beseeching Christ's mercy. "Go show yourselves to the priests," our Lord instructs them (that is, they need to be examined by the religious authorities and declared clean). And so it came to pass that "as they went, they were cleansed."
Now while all ten lepers were healed, only one (a Samaritan--an outcast among the outcasts) turned back to give thanks. The other nine were no doubt thankful to be healed--but it never did seem to occur to them to thank the One Who had healed them.
It is easy for the likes of us to accuse the nine of being ungrateful, but think: how often do you and I take for granted the multitude of blessings God has so graciously bestowed upon us? We are quick to grumble and complain when things aren't going our way--but seldom do we fall down upon our knees before Him to praise Him, thanking Him from the bottom of our hearts for the innumerable good gifts he grants to us--unworthy sinners though we are.
Do we think to thank God when we awaken in the morning for the mere fact that we are still alive and have been given another day to love and to serve Him, and to sincerely repent for transgressing again and again His holy commandments? Do we thank Him for the sun, moon and stars--for the very air we breathe? The angels in heaven sing ceaseless praises to God, while we cast the blame on other people or circumstances for our own misfortunes and fail to see how every moment of every day we are sustained by God's providential care.
All ten lepers were cleansed, but only to the one who returned to give thanks did our Lord say, "Arise, go on your way: your faith has made you whole." Surely God makes his sun to shine on both the righteous and the unrighteous, the just and the unjust: but only to those who are truly thankful does He bestow His greatest blessing--true and eternal life as sons and daughters of God in His heavenly Kingdom.