23 “There shall the sparrows build their nests: their leader is the house of the coot”. Where shall the sparrows build? In the cedars of Libanus....Who are the sparrows? Sparrows are birds indeed, and fowls of the air, but small fowls are wont to be called sparrows. There are therefore some spiritual ones that build in the cedars of Libanus: that is, there are certain servants of God who hear in the Gospel, “Sell all that you have, and give to the poor; and you shall have treasure in heaven; and come and follow Me.”...Let him who has resigned many things, not be proud. We know that Peter was a fisherman: what then could he give up, to follow our Lord? Or his brother Andrew, or John and James the sons of Zebedee, themselves also fishermen; and yet what did they say? “Behold, we have forsaken all, and followed You.” Our Lord said not to him, You have forgotten your poverty; what have you resigned, that you should receive the whole world? He, my brethren, who resigned not only what he had, but also what he longed to have, resigned much....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)