Vowing in a time of distress

בפסוק וידר יעקב נדר לאמר שיהי' נודרין בעת צרה.

On the passuk "And Yaakov vowed a vow, saying" (Bereishis 28:20) - that one should make a neder (vow) in a time of distress.

The Sefas Emes derives from Yaakov's vow the practice of taking on a vow or resolution specifically when one is in a time of trouble (eis tzarah).

זה הענין שתיקן ת"ע היינו שע"י הקבלה בלב שנודרין ומשתוקקין לבוא לרווחה כדי לעבוד ה' יהיו נושעים גם בעת צרה:

This is the matter that the "Tikkun" [of the seventy elders / the established practice] instituted - namely, that through the acceptance in the heart, in which one vows and yearns to come to relief in order to serve Hashem, one will be saved even in a time of distress.

By making a heartfelt commitment in one's time of trouble - longing for relief not for its own sake but so that one will be free to serve Hashem - a person draws down salvation even from within the distress itself; the sincere inner resolve to use the yeshuah for avodas Hashem is what brings the rescue.

Summary: From Yaakov's vow we learn that in a time of distress one should make a heartfelt neder, yearning for relief specifically in order to serve Hashem - and this inner commitment is itself what draws down salvation.