What is the meaning of "she'Lo Sidor"?
Rashbam: He does not vow at all.
Seforno: He does not accustom himself to vowing. If he will be used to vowing, sometimes he will not pay, and he will sin. This is like increasing Tefilah - sometimes his intent departs, and he has sin.
What is the meaning of "mishe'Tidor v'Lo Seshalem"?
Metzudas David: It is to vow and not pay immediately. Perhaps over time he will regret [the vow, and not fulfill it]!
What is the best conduct about vows?
Nedarim 9a #1: "It is better not to vow
Rosh (9a): Had our verse said only "it is better not to vow than to vow", we would explain 'than to vow and not pay.' "And not pay" is extra, so it is as if the verse discusses one who vows and pays, and one who vows and does not pay, and it says that it is better not to do either of these.)
