At the very end of this week's parsha, Avraham is commanded to circumcise himself and the members of his household. The Torah tells us, "And he circumcised the flesh of their foreskin on that very day" (Bereishis 17, 23). Rashi explains that on the very day that Avraham was commanded he fulfilled the mitzvah. Moreover, he didn't wait for the night to circumcise himself, rather, he did it during the daytime and was not afraid from the gentiles and scoffers.
Rav Wolbe (Shiurei Chumash) elaborates on Rashi's explanation. Elsewhere Rashi writes that anytime the Torah writes "on that very day" the Torah is implying that despite the fact that there was something to fear, nevertheless, the act was carried out openly in clear sight of all without any negative repercussions. In Avraham's generation there were those who threatened to prevent any attempt of his circumcision, and there were others who ridiculed him for performing Hashem's commandments. We might add that he was in his eighties at the time of the commandment and such a procedure could be very dangerous for someone his age. Yet, not only did these obstacles not hinder his performance of the mitzvah, they didn't even delay him for a few hours to perform it at a more opportune time! When it came to the fulfillment of Hashem's mitzvos, Avraham asked no questions and looked for no excuses.
The lesson to be learned is clear. How many times do we refrain from performing a mitzvah, going to daven, or leaving to learn Torah for fear of what others might say or think? How often do we push off a mitzvah to a seemingly more opportune time for the sake of convenience? Chazal tell us, "When a mitzvah comes to your hand, don't let it become sour." If one hesitates in his performance of mitzvos, it is very possible that he might lose the opportunity altogether, whereas if he grabs the opportunity he has earned a mitzvah worth more than its weight in gold.