4 And your Lord says unto you, “What shall be given you, or what shall be set before you, against the deceitful tongue?”. What shall be given you, that is, as a weapon to oppose to the deceitful tongue, to guard yourself against the deceitful tongue? “Or what shall be set before you?” He asks to try you: for He will answer His own question. For He answers following up his own inquiry, “even sharp arrows of the Mighty One, with coals that desolate, or that lay waste”. They that desolate, or that lay waste (for it is variously written in different copies), are the same, because by laying waste, as you may observe, they easily lead unto desolation. What are these coals? First, beloved brethren, understand what are arrows. The “sharp arrows of the Mighty One,” are the words of God...What then are the “coals that lay waste?” It is not enough to plead with words against a deceitful tongue and unrighteous lips: it is not enough to plead with words; we must plead with examples also...The word coals, then, is used to express the examples of many sinners converted to the Lord. Thou hear men wonder, and say, I knew that man, how addicted he was to drinking, what a villain, what a lover of the circus, or of the amphitheatre, what a cheat: now how he serves God, how innocent he has become! Wonder not; he is a live coal. You rejoice that he is alive, whom you were mourning as dead. But when you praise the living, if you know how to praise, apply him to the dead, that he may be inflamed; whosoever is still slow to follow God, apply to him the coal which was extinguished, and have the arrow of God's word, and the coal that lays waste, that you may meet the deceitful tongue and the lying lips.
5. “Alas, that my sojourning has become far off!”. It has departed far from You: my pilgrimage has become a far one. I have not yet reached that country, where I shall live with no wicked person; I have not yet reached that company of Angels, where I shall not fear offenses. But why am I not as yet there? Because sojourning is pilgrimage. He is called a sojourner who dwells in a foreign land, not in his own country. And when is it far off? Sometimes, my brethren, when a man goes abroad, he lives among better persons, than he would perhaps live with in his own country: but it is not thus, when we go afar from that heavenly Jerusalem. For a man changes his country, and this foreign sojourn is sometimes good for him; in travelling he finds faithful friends, whom he could not find in his own country. He had enemies, so that he was driven from his country; and when he travelled, he found what he had not in his country. Such is not that country Jerusalem, where all are good: whoever travels away from thence, is among the evil; nor can he depart from the wicked, save when he shall return to the company of Angels, so as to be where he was before he travelled. There all are righteous and holy, who enjoy the word of God without reading, without letters: for what is written to us through pages, they perceive there through the Face of God. What a country! A great country indeed, and wretched are the wanderers from that country.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)