משלי, פרק כ״ז, פסוק א׳

Human nature often drives people to make grand plans and feel a sense of absolute certainty about the future. Yet, reality can shift in an instant. The primary approach among commentators is that one must avoid boasting and self-praise regarding future achievements or positive events. Even if an individual currently possesses all the necessary resources and abilities to carry out their plans, they must guard against such overconfidence [אלשיך].

From a slightly different angle, this caution applies directly to the performance of commandments and good deeds, such as giving charity. A person should never delay doing good by promising to take care of it tomorrow. Instead, one must act immediately, embracing the mindset of seizing the present moment rather than relying on the future [אבן עזרא].

The underlying reason against boasting lies in the absolute unpredictability of time. Through a poetic metaphor, time itself is depicted as becoming pregnant and giving birth to new, unfolding occurrences [עמנואל הרומי, מצודת ציון, מלבי״ם]. Because the hazards of life renew themselves constantly, a person cannot possibly know what the current day will bring forth, let alone control a tomorrow that does not yet belong to them [מלבי״ם]. There is always the risk that today might give rise to sudden hardship or an unexpected turn of events, entirely unraveling a person's intentions and canceling their plans for the future [רש״י, רלב״ג, מצודת דוד].