“rash.” The Hebrew word is bahal (#0926 בּהל), and in the Piel form, as it is here, it has two meanings; to dismay or terrify; and also to act hastily or be hurried. Both meanings are true in Ecclesiastes 5:2. Although most modern versions are leaning toward “hasty” or “quick,” in part because the second phrase of the verse is about being hasty before God, the aspect of words that dismay or cause fear is an important meaning of the word, arguably the most import meaning. If we are not hasty with our mouth, many times we will not be rash or hurtful either. Thankfully, the English word “rash” can include both the meaning hasty and hurtful.
People should not be quick or hurried in what they say, but should think through their words. We are each responsible to make sure that our words are godly and that we speak the truth in love (Eph. 4:15), and that what we say benefits the hearer (Eph. 4:29). The whole point of the phrase, “For God is in heaven and you are on earth,” is that God is our heavenly judge and He hears us and will hold us accountable for what we say. Jesus warned us about what we say: “And I say to you, that every careless word that people speak, they will give account of it on the Day of Judgment” (Matt. 12:36). It is in our power to speak in a godly way, which will result in blessings for both ourselves and others.
The book of James also has a lot to say about speaking, and has a number of parallels to Ecclesiastes. For example, James 1:19 says to be quick to listen and slow to speak.
“utter a word.” The Hebrew is more literally, “bring up (or “out”) “a word,” but the meaning of “word” can be quite broad. The NAB suggests a promise, which is certainly included by the fact that what is spoken is the sacrifice of fools, and fools promise many things to God that they do not really have any intention or means to fulfill. The Hebrew can also mean “bring up a matter,” as if the person was going to bring up something to God for consideration.