Avraham's Real Estate Negotiations: A Final Test

Many of the meforshim wonder why the Torah needed to go into such great detail when telling us about Avraham's acquisition of a burial plot for Sara. Why not simply tell us that when Sara passed away, Avraham bought Me'arat Ha'machpeila from Ephron?
The classic answered offered by the Midrash (Breishit Rabbah 79:6) is that the Torah wanted the transaction put on record in case anyone ever disputed Bnei Yisrael's claim to the land. The Midrash goes on to say that this explains why we are told that David Hamelech purchased the land that the Beit Hamikdash stood on (Divrei Hayamim I 21:25) and that Yaakov purchased land in Shechem, the eventual burial place of Yosef (Breishit 33:19). Hashem knew that at some point in the future other people would dispute Bnei Yisrael's claim to these lands and therefore He wanted a historical record of their purchase.
The Ramban however offers a different approach. In one of his explanations for the necessity of this story he writes (Breishit 23:19),

ונכתבה זאת הפרשה להודיע חסדי השם עם אברהם שהיה נשיא אלהים בארץ אשר בא לגור שם והיחיד, וכל העם היו קוראין לו "אדוני", והוא לא אמר להם כן שהיה שר וגדול, וגם בחייו קיים לו ואגדלה שמך והיה ברכה
And this section was written to inform us of the kindness of Hashem toward Avraham that he was a prince of God in the land in which he came to settle and he was unique. And the entire nation referred to him as 'My Master', and he never told them that he was an officer or great person. In his life the blessing was fulfilled that his name would become great and it would be for a blessing

According to Ramban the importance of this story is contained within the periphery. The fact that Avraham bought a burial plot for his wife is immaterial; what is important is the fact that God's blessing started to come true in Avraham's lifetime because the people honored him and treated him as God's prince.
The Chizkuni however offers a different approach, which directly contradicts the Ramban's claim. The Chizkuni notes that when Avraham initially spoke to the Bnei Cheit about purchasing a burial plot he, "rose up and bowed down" (23:7). On this the Chizkuni comments,

ויקם אברהם וישתחו אברהם היה צריך לכולן שאפי' מכר לו עפרון את השדה לא היה אברהם רשאי לעשותו בית הקברות שלא ברשות כל בני העיר ולכך הוצרך לקום כדי להשתחוות לכולם אפי' לאותם של אחוריו. אבל בהשתחות לעפרון שהיה יחידי לא הוצרך לקום אלא להשתחות לפניו.
Avraham rose up and bowed down. Avraham needed to do both of these because even if Ephron sold him the field Avraham would not have been permitted to convert it into a cemetery without the permission of all of the townspeople. Therefore he need to rise in order to bow down to all of them, even those who were behind him. But when he bowed down to Ephron, who was but one individual, he did not need to rise, rather he bowed down before him.

According to Chizkuni, even if Avraham was known as a prince, as Ramban writes, he still needed to grease the palms of the local zoning board or else he would not have been able to bury Sara where he wanted to. According to the Ramban, Avraham did not have a difficult time finding a resting place for Sara - he was a prince and the locals were honored to sell him the land. However, according to Chizkuni, Avraham did not receive any preferential treatment and needed to go through the political process just like anyone else.
The explanation of the Chizkuni fits in well with a Midrash (Midrash Ha'Gadol), which explains that the need to purchase a burial plot for Sara was yet another test of Avraham's belief and dedication to Hashem. Writes the Midrash,

בוא וראה ענוותנותו של אברהם אבינו! שהבטיחו הקב”ה לתת לו ולזרעו את הארץ עד עולם ועכשיו לא מצא קבורה אלא בדמים מרובים, ולא הרהר אחר מידותיו של הקב”ה ולא קרא תגר, ולא עוד אלא שלא דיבר עם יושבי הארץ אלא בענוה, שנאמר: “גר ותושב אנכי עמכם” - אמר לו הקב”ה: אתה השפלת עצמך, חייך שאני אשימך אדון ונשיא עליהם.
Come and see the humbleness of Avraham Avinu! God had promised to give him and his offspring the Land and now he could only find a burial place for a large sum of money and he did not question the ways of the Holy One Blessed be He and he did not rebel; not only that, but he even spoke to the locals with humility, for it says, 'I am an alien and resident among you' - The Holy One Blessed be He said to him: You lowered yourself, I swear that I will make you a master and prince over them.

According to the Midrash, this entire chapter is a test of Avraham's will. God had commanded him to leave his homeland and he listened. God had brought a famine to Canaan, forcing him to leave for Egypt and his faith never wavered. God had commanded him to sacrifice his beloved son and he was willing to go through with it. Then his wife died and he wanted to bury her in the Land that God had promised to give him, but he had to pay a large sum of money for a small piece of the Land that was supposed to be his. Avraham could have said, "Enough is enough! I was willing to sacrifice my own son, why do I deserve this?" But he did not. As the Chizkuni and the Midrash teach us, he went through with the ordeal of purchasing the plot of land just like anyone else. The Torah goes into such great detail about this business transaction to show us Avraham's humility in passing yet another test; Avraham got approval both from the local zoning board and from Hashem.