13. The next words of the pasuk are בידכם ומקלכם. Following the path of remez, the Sar Shalom explains that מקלכם means "your leniencies." The Torah tells us, בידכם מקלכם, take these leniencies into your hands. Get a grip on yourselves and on the situation, and stop being lenient in the areas where you should be stringent.
14. לכם הזה החדש teaches us that the dates of the calendar are dependent on the determination of beis din. When beis din declares it rosh chodesh, it is rosh chodesh. When they announce a leap year, it becomes a leap year.
The Midrash comments on that, "Everything is in our hands! Everything is in our possession." The Chidushei HaRim zy"a says, "If a person would know what this means, and what is in his hands, he wouldn’t waste a minute." He can accomplish so much with his tefillos and mitzvos. If he knew what he accomplishes, he would be very active in avodas Hashem at all times.
