Matot 

מטות

The Sages disagreed with regard to what is preferable: To state vows and fulfill them, or to refrain from stating vows altogether. 

[“That which you vow, pay;] it is better that you not vow than that you vow and not pay” (Ecclesiastes 5:3–4). Better than both this and that [one who vows and pays and one who vows and does not pay] is one who does not vow at all; this is the statement of Rabbi Meir. Rabbi Yehuda says: Better than both this and that [one who does not vow and one who vows and does not pay] is one who vows and pays. Rav Dimi brother of Rav Safra teaches: With regard to anyone who states a vow, even if he fulfills it, he is called a sinner. Rav Zevid said: What verse teaches this? “If you will refrain from vowing, there will be no sin in you” (Deuteronomy 23:23). One can infer: If you did not refrain from stating vows, there is sin. <source>(<i>Nedarim</i> 9a, 77b) </source>