Abraham's final resting place alongside his wife marks the end of his physical journey, yet the details surrounding this plot of land carry deep significance for his descendants. Whenever the burial in this specific cave is brought up, the fact that the field was purchased is always highlighted.
This repetition is highly intentional and serves to showcase Abraham's deep faith. God had promised to give the entire land to him and his family, yet Abraham still had to buy a place just to bury his dead. Despite this reality, he never questioned God's promise or complained about having to purchase the land [רד״ק, ברכת אשר].
At the same time, continually stressing the legal purchase acts as a firm guarantee for future generations. It proves that the early leaders of the family truly recognized this land as their own, which is why they chose to establish their eternal resting place there [רש ר הירש]. They made this legal acquisition with the clear goal that the generations following them would also be buried in that very spot [ביאור שטיינזלץ].