What are the verses indicating vows, and is expiation obligatory for one who is unable to fulfill a vow? What is its expiation and consequence? Or is making vows forbidden?

The evidence for the obligation to fulfill vows is found in the texts of the Qur’an and the Sunnah, such as His —the Most High— saying: "And let them fulfill their vows," and "They fulfill vows," and the saying of the Prophet, peace and blessings be upon him: "Whoever vows to obey Allah, let him obey Him; and whoever vows to disobey Allah, let him not disobey Him."