´It was narrated that Ibn 'Abbas said:` "The Messenger of Allah passed by a man who was leading another man by a rope. The Prophet took it, and cut it, and he said: 'It is a vow.'"
Explanation & Benefits
Hafiz Muhammad Ameen
It is obligatory to fulfill a vow (nadhar) that pertains to an act of righteousness and nearness (to Allah). However, a vow of this kind, from which nothing is gained except hardship and humiliation—neither does the one who makes the vow benefit, nor does anyone else—this is a meaningless vow. Such a vow should not be fulfilled because it is without benefit.
Source: Sunan Nasa'i: Translation and Benefits by Shaykh Hafiz Muhammad Amin Hafizullah, Page: 3841