“The L-RD, the G-d of heaven, who took me from my father’s house, and from the land of my nativity, and who spoke unto me, and who swore unto me, saying: Unto thy seed will I give this land; He will send His angel before thee, and thou shalt take a wife for my son from thence.” – Genesis 24:7, JPS 1917 Tanach
“Therefore, I know that He will send His angel to make Your way prosper, to fulfill His promise to me.” – Rashbam, sefaria.org
When the time arrived for Abraham to find a wife for his son, Isaac, Abraham sent his trusted servant Eliezar on the mission, back to the land where Abraham had lived. Abraham explained to Eliezer that H’Shem would “send his angel” before him on the journey. When Eliezer arrived, he prayed, “‘O L-RD, the G-d of my master Abraham, send me, I pray Thee, good speed this day, and show kindness unto my master Abraham” (Genesis 24:12, JPS 1917 Tanach). In this manner, he prayed in the merit of Abraham, as per the tradition even today, regarding the prayers of the chassidim, in the merit of their Rebbes.
What is fascinating to note, is that within this parashas, there is another mentioning of prayer in the merit of a righteous person. Preceding Eliezer’s return, “Isaac went out to meditate in the field at the eventide; and he lifted up his eyes, and saw, and, behold, there were camels coming” (Genesis 24:63, JPS 1917 Tanach). Tradition infers that the field where Isaac meditated, i.e., “prayed,” was the field of the cave of Machpelah, where Sarah was buried. Therefore, commentary speaks of him, praying in the merit of his mother (the matriarch of the Jewish people) for Eliezer’s mission to be successful.
“The angel of the L-RD encampeth round about them that fear Him, and delivereth them.”
– Psalm 34:8, JPS 1917 Tanach