Four hundred shekels of silver, in negotiable currency (Gen. 23:16)
The Torah foresaw the future difficulties Jews would have defending their rights to their holy sites. The Torah therefore devotes much time detailing the transaction by which Abraham acquired the Cave of Machpela, and the exact sum he spent to purchase it. (Drashot El-Ami)
Who ruled over all that he had (Gen. 24:2)
These words refer to Abraham and indicate just how great a person he was. Though Abraham amassed wealth, he did not become like some other wealthy people for whom money becomes the only motivating factor in their lives. Abraham ruled over his possessions, and not the other way around. (Klai Yakar)
And Isaac went out to meditate in the field (Gen. 24:63)
Rashi explains that the word "meditate" means "to pray--as if pouring forth the contents of one's heart." If such is the case, why didn't the Torah explicitly state that Isaac went out to pray in the field?
We are supposed to take a lesson for our general conduct from the way Isaac prayed. A person should not call attention to himself and publicly announce his fear of Heaven. Rather, we should conduct ourselves as Isaac did--quietly, and without fanfare. A passer-by would have thought that Isaac was only strolling in the field, when in reality he was composing the afternoon prayer. (Leket Amarim)