Part of being truthful is keeping one’s word. For in addition to the sin of it, it is simply disgraceful to renege on one’s word. The Sages thus said: “He Who punished the generation of the Flood and the generation of the Dispersion, He will take vengeance of him who does not stand by his word” (Bava Metzia 44a). Therefore one should think very carefully before letting any commitment out of one’s mouth to see whether he will be able to keep what he says. And if one already let a commitment out of his mouth — he should keep it, viewing it as though he took a [full-fledged] oath about it.
And since our holy Torah is Toras Emes — the Torah of truth — it is imperative that we learn it truthfully, to acknowledge the truth [when our understanding is proven wrong], and to accept the truth no matter who says it, even that person is the smallest of the small. This is the straight path for those who walk honestly, and in this way the person will find favor and goodly wisdom in the eyes of God and man (Mishlei 3:4).