Bird's-eye view
The book of Proverbs is intensely practical, giving us divine wisdom for the grit and friction of everyday life. A central theme, hammered on repeatedly, is the stark contrast between the wise man and the fool. This contrast is not primarily about IQ points or academic credentials; it is a moral and spiritual distinction. The fool is not necessarily a dullard; his folly is ethical, rooted in a heart that is turned away from the fear of the Lord. And one of the most consistent ways a fool reveals his folly is by opening his mouth. This particular proverb gives us a piece of tactical, observable wisdom. It is a mercy from God, showing how even a fool can stumble into the appearance of wisdom, and in so doing, perhaps begin to learn the first thing about acquiring the substance of it.
Commentary
28 Even an ignorant fool, when he keeps silent, is considered wise; When he closes his lips, he is considered understanding.
We have a well known saying in English that gets at the same principle: "It is better to keep your mouth shut and be thought a fool, than to open it and remove all doubt." The Holy Spirit said it here first, and with more precision. This is a glorious piece of practical advice that works on multiple levels. It is, on the one hand, a simple observation about human interaction and reputation management. But underneath that, it is a pointer to the very nature of wisdom and folly.
Let's take it clause by clause.
Even an ignorant fool, when he keeps silent, is considered wise...
The subject is the fool. In Proverbs, the fool is not someone who can't pass a test. He is the one whose heart is corrupt, who says in his heart there is no God (Ps. 14:1). His problem is rebellion, not a lack of raw intellect. Folly is bound up in his heart (Prov. 22:15). And what is in the heart inevitably comes out of the mouth (Matt. 12:34). The fool's default setting is to pour out folly (Prov. 15:2). He multiplies words, but has nothing to say (Eccl. 10:14). So when a man who is constitutionally a fool manages to do something as unnatural for him as keeping his mouth shut, something remarkable happens. He is "considered" wise. The Hebrew word is chashab, which means to reckon, to impute, to account. It's an accounting term. Wisdom is credited to his account, not because he has actually earned it, but because he has stopped broadcasting the deficit.
This is a great mercy. God has built the world in such a way that there is a brake pedal available even for the fool. By simply ceasing to talk, he can be "spotted" some wisdom. He is given the benefit of the doubt. People can't see the churning foolishness in his heart if the door of his lips is kept shut. This silence can be a constructive thing. It is hard to learn anything while you are talking. It is impossible to observe how others are reacting, or what God is doing, when you are busy thinking about what clever thing you are going to say next. So, for the fool, this silence is not just a mask; it is his only opportunity to begin the path toward actual wisdom.
When he closes his lips, he is considered understanding.
The second clause reinforces the first, as is common in Hebrew poetry. Closing the lips is parallel to keeping silent, and being considered a man of understanding is parallel to being considered wise. But there is a slight intensification. Understanding (binah) points to discernment, the ability to distinguish between things. The silent fool is not just thought of as having generic wisdom, but as having the specific quality of discernment. People will assume he is weighing matters carefully. They will project their own intelligence onto his quiet demeanor. They will think, "Ah, here is a thoughtful man, a man who does not speak rashly."
Of course, the proverb is describing an appearance, a reputation. It does not say the fool becomes wise by shutting up. It says he is considered wise. The application for the fool is obvious: talk less. But the application for the wise is to be discerning about silence. Not every quiet person in the room is a deep thinker. Some are just fools following this very proverb, whether they know it or not. We are to be shrewd as serpents. But the primary thrust is a commendation of verbal restraint. In a world drowning in noise, chatter, and endless opinions, the man who has mastered his tongue has mastered a great thing indeed (James 3:2). This proverb gives the first, remedial lesson in that school of mastery.
Application
So what do we do with this? First, we must all recognize our inner fool. All of us are prone to speak when we should listen, to offer an opinion when we have no knowledge, and to broadcast our ignorance. Sin has made fools of us all. Our natural state is to be yammering fools, which is why we must be born again into a new kind of life, a life governed by the Spirit of Christ, who is the wisdom of God (1 Cor. 1:24).
Second, this proverb is a call to cultivate the discipline of silence. This is not a call to become mute, but to be deliberate in our speech. Before you speak, ask yourself if what you are about to say improves on the silence. Is it true? Is it kind? Is it necessary? Too often, our words are just noise, the overflow of a restless and foolish heart. Restraining our lips is a fruit of the Spirit, an aspect of self control. It is a practical outworking of humility, recognizing that we do not need to be the narrator of every event.
Finally, we must remember that this proverb, like all proverbs, points beyond itself to Christ. Jesus is the ultimate fulfillment of this. He was the truly wise man who knew when to be silent. Before His accusers, as a sheep before its shearers is silent, so He opened not His mouth (Is. 53:7). His silence was not an absence of an answer, but the presence of perfect, resolute wisdom. He was silent so that we, the babbling fools, could be forgiven. He took our foolishness upon Himself on the cross, and offers us His perfect wisdom in exchange. Therefore, the path to true wisdom is not found first in the technique of closing our lips, but in bowing our knee to the Lord Jesus and confessing our foolishness to Him. When we do that, He begins the work of transforming our hearts, and as a direct result, He will begin to tame our tongues.