Parshat Matos opens:
“And Moshe spoke to the heads of the tribes and to the B’nai Yisrael saying: This is the thing which Hashem has commanded. When a man vows a vow unto Hashem, or swears an oath to bind with a bond (upon) his soul, he shall not break his word; according to that proceeded out of his mouth he shall do.” (Sefer Bamidbar, Perek 30, posukim 1-3)
From there, our Parsha informs us about the specific laws concerning vow, oaths, nedarim.
R’ Zelig Pliskin, in “Growth Through Torah” (page 366) brings a lesson regarding silence from our Parsha citing Sefer Bamidbar, Perek 30, posuk 15: