I say, and with God's success: It does not affect, and zakat is obligatory upon him even if the nisab decreases during the year as long as it does not reach zero; because the decrease of the nisab during the year is considered void, and it is not taken into account, and only the endpoints of the year are considered. If he possesses the nisab at the beginning of the zakat year, it is not a condition for him to maintain ownership of the nisab throughout the year. For example, if he has (100) grams of gold at the beginning of the year, then it decreases during the year, and then returns to (100) grams of gold at the end of the year, then zakat is obligatory upon him. However, if he has (100) grams of gold at the beginning of the year, and then it reaches zero during the year, then he begins a new year when he possesses the nisab again. Refer to: Al-Mishkat in the rulings of purification, prayer, and zakat, p. 321, and God knows best.