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)