Some examples of Nazar / vows in the Qur'an

إِذْ قَالَتِ ٱمْرَأَتُ عِمْرَٰنَ رَبِّ إِنِّى نَذَرْتُ لَكَ مَا فِى بَطْنِى مُحَرَّرًۭا فَتَقَبَّلْ مِنِّىٓ ۖ إِنَّكَ أَنتَ ٱلسَّمِيعُ ٱلْعَلِيمُ

Behold! a woman of 'Imran said: "O my Lord! I do dedicate unto Thee what is in my womb for Thy special service: So accept this of me: For Thou hearest and knowest all things."

فَكُلِى وَٱشْرَبِى وَقَرِّى عَيْنًۭا ۖ فَإِمَّا تَرَيِنَّ مِنَ ٱلْبَشَرِ أَحَدًۭا فَقُولِىٓ إِنِّى نَذَرْتُ لِلرَّحْمَٰنِ صَوْمًۭا فَلَنْ أُكَلِّمَ ٱلْيَوْمَ إِنسِيًّۭا

"So eat and drink and cool (thine) eye. And if thou dost see any man, say, 'I have vowed a fast to (Allah) Most Gracious, and this day will I enter into not talk with any human being'"