2) The Netziv writes that although Avraham was legally entitled to the spoils of war gotten in the battle against the kings, it would smack of a lack of yashrus to benefit from monies obtained in that way and so he would not take a penny.
Let's contrast that with current events: The system that manages EBT transactions (food stamps) went down this weekend and for a short time there was no limit on purchases. Hundreds of shoppers literally cleaned out two Walmart stores, almost starting a riot. A news story reports, “Shoppers gave mixed reactions to the incident, with one man in the Springhill store told KSLA it was simply "human reaction" to stock-up when given the opportunity.” In other words, it’s “human nature” to be a ganav.
3) A vort from the Radomsker: “Motza sefasecha tishmor ka’asher nadarta…” Sometimes a person takes an appeal to heart and makes a promise to help or a commitment to do something. However, as time passes, enthusiasm wanes; it becomes hard to write that check or make the time to take action for the cause one was once so passionate about. The Torah is telling us, “Motzah sefasecha tishmor,” fulfill your promises, “Ka’asher nadarta,” with the enthusiasm and zeal you had when you made the initial commitment.
That’s what characterized the behavior of Avraham Avinu. “Vayeilech Avram,” (12:4) Avraham’s journey on day 100 was carried out, “Ka’asher dibeir eilav Hashem,” exactly with the same excitement as on day #1 when G-d first spoke with him. “Vayamal Avraham es Yitzchak b’no… ka’asher tzivah o’so Elokim.” (21:4) Avraham had the same enthusiasm and zeal when doing milah on Yitzchak as he had when he first got the commandment. (See here ("Va'yar" in the second column) for how the Radomsker uses this to explain the first pasuk/Rashi on our parsha.)