Isaiah 55:10-11 forms part of an invitation to life through sincere repentance. The word of God is such that whether one likes it or not, it will restore peace to Israel. But only those who will approach God will enjoy its benefits.
The passage immediately follows God's declaration that His thoughts and ways are far above men's thoughts and ways. He is the Holy One after, the completely other, whom no man can put in a box and treat as if He is like any man. This loftiness, is matched by His desire to be "With-Us", expressing His will in such a way that it works like the rain and snow that from heaven waters the earth.
The basic image employed here is the natural cycle of rain and evaporation. Clouds in heaven produce rain and snow that water the earth, flowing into streams and rivers, irrigating the soil and along the way give drink to plants and animals. These latter in turn, give their "products" to man, grain and wheat, milk and meat. When the waters have run their course, they go back into the sea whence they are carried back in vapors to heaven.
God's Word is an event. It is DABHAR, a happening first, and then something remembered and recalled in proclamation before it is written down to become "scriptures". Isaiah's Book of Consolation (Isaiah 40-55) is a recollection of past events that give rise to hope in God's actions in the future. As God was faithful to His covenant with David in the past, so shall He undo Himself in showing forth his fidelity. Verse 11 leads to verses 12-13, a vision of Israel's restoration, to peace, to life bursting forth where there has been death.
Isaiah 55:10-11 is one of the passages that is repeatedly read in the liturgy. It is always read on Tuesday in the first week of Lent and in the fifteenth Sunday of Year A. As part of Isaiah 55:1-11, it is read during the Easter vigil.
The Church uses it in Lent, highlighting the journey of the Word of God from the bosom of the Father to His work among men, and the completion of that work on the Cross ("It is finished") giving life to all, like the grain of wheat that falls to the ground (cf. John 12).
In the Easter vigil, it is part of the readings that prepare those who are to be baptized and those who will renew their baptismal vows. The Word of God after all, is the seed that brings about new life in God's vineyard (cf. 1 Peter). The call to repentance is the renewed invitation to live according to the dignity of those who are called from darkness into light, death to life.
The fifteenth Sunday of Ordinary Time (A) pairs the selection with Matthew's narrative of the sower and the seed. The proclamation of the Gospel which is the Word of God bears fruit depending on the soil that receives it. It must be "good soil" -- not one under Satan's power, nor one that is shallow, nor one filled with the anxieties of this age.
Isaiah 55:10, finally is quoted by Paul in 2 Cor. 9:10 as he exhorts his community of faith to be generous in their contributions to the Mother Church, assured that God does not ignore a generous act.
