The Prophet (ﷺ) forbade making vows, and said, "It does not bring good. Indeed, it is only a means by which something is extracted from the miserly."[Agreed upon].
Oaths and Vows - Bulugh al-Maram 1384
This prohibition from the Prophet (ﷺ) regarding vows contains profound wisdom. Vows do not bring about additional good that Allah has not already decreed. Rather, they may lead a person to distress when fulfilling them becomes burdensome.
Scholarly Commentary
The Messenger (ﷺ) described vows as extracting something from the miserly because the miserly person only gives charity or performs acts of worship when compelled by a vow. Without the vow, they would withhold their wealth from righteous causes.
Scholars explain that while vows are generally discouraged, if one makes a vow to obey Allah, it becomes obligatory to fulfill it. The prohibition here refers to making vows a habitual practice or using them to compel oneself to do what should be done voluntarily.
Ibn Hajar al-Asqalani notes in his commentary on Bulugh al-Maram that the wisdom behind this teaching is to preserve the purity of intention in worship, ensuring acts are done sincerely for Allah rather than as fulfillment of self-imposed obligations.