“That which is gone out of thy lips thou shalt observe and do; according as thou hast vowed freely unto the L-RD thy G-d, even that which thou hast promised with thy mouth.”
– Deuteronomy 23:24, JPS 1917 Tanach
The Torah records the positive commandment to observe whatever commitments we speak of through our own words. Although it is not advisable to make a vow these days, we are to be careful about fulfilling the promises we make with ourselves and others through our spoken words. “I will perform unto Thee my vows, which my lips have uttered, and my mouth hath spoken” (Psalm 66:13-14, JPS).
Otherwise, we will be held accountable for not following through on our words. Of course, this only applies to kind speech and intentions, whereas if we have said anything hurtful to another person, we should apologize in due time, and certainly not act upon anything said hastily, that could have negative consequences if acted upon. G-d forbid.
Positive speech is recommended at all times, when speaking to others, as well as when speaking of others. It is better to bless than to curse; i.e., it is better to speak well of people, than to speak ill of them. When we consider our words, before speaking, we should refrain from saying anything negative. “Set a guard, O L-RD, to my mouth; keep watch at the door of my lips” (Psalm 141:3, JPS). “Keep thy tongue from evil, and thy lips from speaking guile” (Psalm 34:14, JPS).
Additionally, even our thoughts should be pure, as exemplified by the following pasuk (verse), “Thou hast tried my heart, Thou hast visited it in the night; Thou hast tested me, and Thou findest not that I had a thought which should not pass my mouth” (Psalm 17:3, JPS 1917 Tanach). For as we think, will be as we act; unless, we can scrutinize our thoughts, reconfigure our intentions, and not act upon our unconscious motives, without reflecting upon our actions.