Avraham told Eliezer that his success would already be ensured from the onset, without any difficulties on Eliezer’s end.
Indeed, this is what happened in Eliezer’s mission, as can be clearly seen from the Torah’s account of Eliezer’s undertaking.
After Eliezer had arrived at his destination of Aram Naharaim, the following occurs:
Text 4
And he made the camels kneel outside the city beside the well of water, at eventide, at the time the maidens go out to draw water. And he said, "O Lord, the G-d of my master Avraham, please cause to happen to me today, and perform loving kindness with my master, Avraham. Behold, I am standing by the water fountain, and the daughters of the people of the city are coming out to draw water. And it will be, [that] the maiden to whom I will say, 'Lower your pitcher and I will drink,' and she will say, 'Drink, and I will also water your camels,' her have You designated for Your servant, for Yitzchak, and through her may I know that You have performed loving kindness with my master." Now he had not yet finished speaking, and behold, Rivka came out, who had been born to Besuel the son of Milcah, the wife of Nachor, Avraham's brother, and her pitcher was on her shoulder.
Bereishis 24:11-15
The first instance where G-d’s assistance is recognizable, is seen at the moment of Rivka’s entry. Before Eliezer even finishes his prayers, Rivka already appears before him.
While one might assume that Eliezer was indeed a participant in causing Rivka to come to the well, as Rivka’s arrival was in answer to his prayers—which is expressive of his participation—this is not the case.
From the verse’s statement that, “he had not yet finished speaking, and behold, Rivka came out,” it is indicative that Rivka’s coming out was not as a result of his prayers, but had been predestined to occur beforehand.
Indeed, for Rivka to have arrived at the scene before Eliezer finished his short prayer, G-d must have implanted into her mind the idea to set out to the well before Eliezer even began praying.
The reason that Eliezer needed to pray, and that Rivka’s entry was subsequent to his prayers—though her arrival had already been ensured—was only so that Eliezer would recognize which girl the Almighty had sent.
Once Eliezer had made a sign in his prayers as to know who the proper girl would be, it became easy for him to spot the fitting bride for Yitzchak. His prayers though did not cause the actual event to come about.
Later on in the saga, after Eliezer meets Rivka’s family and asks permission for the marriage to take place, Rivka’s father Besuel attempts to resist to the match.
In immediate response, the angel of G-d sent to ensure that Rivka return with Eliezer, exterminated him.
This event can be observed in the course of the conversation between Rivka’s family and Eliezer:
Originally, Besuel was part of the conversation, even admitting that this match was ordained by G-d, as he states, "The matter has emanated from the Lord. We cannot speak to you either bad or good.”
When the consent was finally given however, we see that Besuel was absent. The verse tells us:
Text 5
And her brother and her mother said, "Let the maiden stay with us a year or ten [months]; afterwards she will go."
Bereishis 24:55
