Musar su Numeri 32:24

לא יחל דברו, ככל היוצא מפיו יעשה . The last four words in this verse appear superfluous, since if we are prohibited from breaking a vow, we must obviously do according to what we have vowed. The moral lesson the Torah wishes to convey is therefore not connected to the laws of vows and oaths, rather the Torah emphasizes that we must keep our word even if what we have said was not said in the form of a promise or vow. Moses told the tribes of Gad and Reuben: "Carry out what you have said" (32,24). Rashi comments that Moses referred to their undertaking to be the spearhead of the Jewish army in their conquest and division of the Land of Canaan west of the Jordan river (32,18). The latter part was something that Moses had not demanded of them. Another statement of intent had been volunteered by those tribes which had not been part of the condition Moses imposed upon them in order to retain their possessions east of the Jordan.