When you read through Genesis 18:1-8, the appearance of these three "men" (two of them being angels in disguise, the middle one most likely being the Angel of the Lord, a Christophany) results in Abraham hurrying and scurrying to serve them. Undoubtedly Abraham's actions can be explained as part of the Oriental culture of hospitality, however the tone of his actions suggests something far deeper and richer. The immediacy of obedience which he exhibited in the circumcision of his entire household in Genesis 17:23,26 is carried over into Genesis 18. Immediate obedience is a sign of growing maturity in the faith. Abraham is described as "running" in 18:2, hurrying in 18:7 and telling his wife to do the same in 18:6-7 with regards to their serving of the Divine Angel of the Lord and his two created angelic companions. Just the mere presence of angels resulted in an increased urgency to obey and serve the Lord. Thus angels are used by God to attend to obedience, but notice a second area, namely...
More specifically, God uses angels to aid in the administering of God's promises and revealed Word to His people. Just as nurses aid in administering medicine or instructing patients on how to take a doctor's prescription, angels do the same. It is the prescription and doctor's instructions that will bring the ultimate cure, with the nurse's facilitating and encouraging the uninformed patient to adhere to the doctor. Likewise angels function to urge and encourage in the taking in of God's Word and adherence to the voice of the Great Physician, Who lone can save, deliver, heal the soul and Whose word alone affects change.
God's promise to Abraham and Sarah of a promised son - Isaac, is the main point of Genesis 18, with the angels functioning to point out to the reader the importance of that truth.Scripture tell us that both the Gospel and the later revealed law of God in Exodus 19 was accompanied with angels. We know from passages such as Psalm 68:18 that many thousands of angels were present around the slopes of Mount Sinai to reinforce the fact of God's majesty and severity of the Law. Just as "flashing lights" atop a police cruiser make more plain to criminals and law abiding citizens alike the presence of justice, angels do the same.
With regards to the the Gospel, we know that God stationed Cherubim at the entry to the Garden of Eden to dissuade Adam and Eve from attempting access to the Tree of Life, so that they would rely upon God's Covenant of grace through the shedding of innocent blood. In Luke 2 we see the Shepherds guarding their flocks by night and be heralded by angelic hosts of the Savior's birth in Bethlehem. Much like highlighters can do in make words in a Bible more plain to a reader, angels are God's highlighters for underscoring the already glorious and brilliant Gospel.
3. Angels can assist in appreciation
Though the Angels never say a word to Abraham following Genesis 18:9, their presence alerts and influences Abraham to engage in discussion with the central figure - The Angel of the Lord. After delivering the Divine promise once again to Abraham, Abraham inquires as to how such a promise will come about, being that he and his wife Sarah are past child bearing years. The Lord, speaking as the Angel of the Lord, replies in Genesis 18:14 "Is anything too difficult for the Lord? At the appointed time I will return to you, at this time next year, and Sarah will have a son.” In Genesis 21:1-3 we read the fulfillment - "Then the Lord took note of Sarah as He had said, and the Lord did for Sarah as He had promised. 2 So Sarah conceived and bore a son to Abraham in his old age, at the appointed time of which God had spoken to him.3 Abraham called the name of his son who was born to him, whom Sarah bore to him, Isaac."
The Angels signal to Abraham and to us the reader that the One Whom we a reading about is not just any angel, but The Angel of the Lord - God the Son in disguise. Just as a monarch's court function to point all the attention to the majesty and authority of the King to carry out his decree, so it is with the angelic realm. Does the monarch need his royal court and stately robes to be the king? No. However to those who do not know him, such trappings communicate to the seeing eye and senses what is already a fact - royalty, majesty and authority. To an even greater extent, angels can in their invisible workings influence us to see and appreciate the Sovereignty of God. Why else in the prophecies of Christ's return do we see angels attending His coming? To highlight what is already fact: His Royalty, Majesty and Authority.
4. Angels can assist in prayer. 18:22-33
The remainder of Genesis 18 depicts the two "men" or angels leaving to do the Lord's bidding in the judgment of Sodom and Gomorrah. At this point in the narrative, the Lord (The Angel of the Lord) and Abraham are left alone. Abraham begins to plea for Sodom, with the classic text on His prayer for mercy in the event that such-and-such a number of righteous people are left in the cities. How do the angels leaving Abraham and the Lord demonstrate their assistance in prayer? Abraham is now able to focus entirely on the One who remains behind. In many other passages, such as Daniel 10 and Jesus in the Garden of Gethsemane in Luke 22, we see angels assisting the saints of God to pray. At times when we are physically and mentally too weak to utter another word, angelic assistance to provide among other things the understanding that God's purposes in Heaven are ready to be deployed on earth.
We have explored today how angels are used by God in specific areas of the Christian life: obedience, apprehending God's Word, appreciation of God's Sovereignty and prayer. I want to close with a quote from the late pastor and scholar James Montgomery Boice on the practical importance of angelic assistance in the Christian life: "From a practical standpoint, if Christian people thought more of angelic protection, they would be less fearful of circumstances and enemies. At the same time our forgetfulness is understandable, for generally angels are not visible to us."1
1. James Montgomery Boice. The Sovereign God - Foundations of the Christian Faith: Volume 1. Intervarsity Press. 1978. Page 221