When Moshe told Bnei Yisrael their obligations to Hashem, their response was: כֹּל אֲשֶׁר־דִּבֶּר יְקֹוָק נַעֲשֶׂה וְנִשְׁמָע, “…everything that Hashem has said we will do and we will obey.” (Ex. 24,7) If everyone undertook to obey, they should have said, “I will do and I will obey.”
This can be better understood according to the Midrash. The Midrash tells us that when each person proclaimed, “we will do and we will obey”, Hashem sent down two angels. One bound weapons around his waist and the other placed a crown upon his head.
Why did they deserve these two gifts? The answer is that the crown he received for his own commitment to obey. The weapons were symbolic for each man’s assuming an obligation to see that his neighbor also obeys.
The plural term used here represents each man’s own assurance to perform and an assurance that he will also see that others obey.
It is not sufficient for us to obey and fulfill the Mitzvot. It is also up to us to see as much as possible that others also obey.