7 Great is the reward He has set before us: in so great a reward as is set before us, let us see what He has commanded us. For enkindled by the reward of so great a promise, and by the love of the reward, let us make ready at once our strength, our sides, our arms, to do His bidding. Is it as if He were to command us to carry heavy burdens, to dig something it may be, or to raise up some machine? No, no such laborious thing has He enjoined you, but has enjoined you only to “refrain” that member which among all your members you move so quickly.
“Refrain your tongue from evil.” It is no labour to erect a building, and is it a labour to hold in the tongue? “Refrain your tongue from evil.” Speak no lie, speak no revilings, speak no slanders, speak no false witnesses, speak no blasphemies. “Refrain your tongue from evil.” See how angry you are, if any one speaks evil of you. As you are angry with another, when he speaks evil of you; so be angry with yourself, when you speak evil of another. “Let your lips speak no guile.”
What is in your heart within, be that spoken out. Let not your breast conceal one thing, and your tongue utter another. “Depart from evil, and do good.” For how should I say, “Clothe the naked,” to him who up to this time would strip him that is clothed? For he that oppresses his fellow-citizen, how can he take in the stranger? So then in proper order, first “depart from evil,” and “do good;” first “gird up your loins,” and then “light the lamp.” And when you have done this, wait in assured hope for “life and good days.” “Seek peace, and ensue it;” and then with a good face will you say unto the Lord, “I have done what You have bidden, render me what You have promised.”
Source: Sermons on Selected Lessons of the New Testament (New Advent)