Gabriel says a phrase with a common theme in the Bible, “The Lord is with you.” Dr. Edward Sri explains, “Many times in the Old Testament the words “The Lord is with you” signaled that someone was being called to a daunting task…one of the most famous stories that illustrates the meaning of ‘the Lord is with you can be found in Exodus, when God called Moses at the burning bush to confront Pharaoh and lead the Israelites out of slavery in Egypt.”
Found Favor with God
Dr. Sri further explains that to be “found favor with God” as Gabriel declares it to Mary is a phrase that occurs throughout the Bible as well. He says, “Noah is the first person in the Bible described as finding favor with God…the next person to find favor with God is Abraham…Similarly Moses…found favor with God, as did David for whom God established a Kingdom.”
So after a grand introduction, Gabriel gets to the heart of the matter with Mary in Luke 1:31-33
31 And behold, you will conceive in your womb and bear a son, and you shall call his name Jesus.
32 He will be great, and will be called the Son of the Most High;
and the Lord God will give to him the throne of his father David,
33 and he will reign over the house of Jacob for ever;
and of his kingdom there will be no end.” 
Of course, naturally, this has a clear typology with a passage in the Old Testament (like phrases highlighted) in direct connection with God’s promise to King David in 2 Samuel 7.
I will make for you a great name…. When your days are fulfilled and you lie down with your fathers, I will raise up your offspring after you, who shall come forth from your body, and I will establish his kingdom. He shall build a house for my name, and I will establish the throne of his kingdom forever. I will be his father, and he shall be my son…And your house and your kingdom shall be made sure for ever before me; your throne shall be established for ever. —2 SAMUEL 7:9, 12-14, 16.”
Pope Benedict references 2 Samuel 7 writing, “The redemption brought by the promised child would be manifested in the definitive establishment of David’s kingship. Permanence had indeed been promised to the Davidic kingdom: “Your house and your kingdom shall be made sure for ever before me; your throne shall be established for ever” (2 Sam 7:16), as Nathan had proclaimed at God’s own behest. Psalm 89 reflects in a disturbing way the contradiction between the definitive nature of the promise and the historical reality of the collapse of David’s kingship: “I will establish his line for ever, and his throne as the days of the heavens. If his children forsake my law … then I will punish their transgression with the rod … but I will not remove from him my steadfast love, or be false to my faithfulness” (vv. 30–34).”
 Sri, 23.
 Ibid, 25.
 The Holy Bible, Revised Standard Version; Second Catholic Edition (San Francisco: Ignatius Press, 2006), Lk 1:31–33.
 Sri, 26.
 Pope Benedict XVI, 30-31.