When the people became negligent as to tithing, the priests and Levites were affected. That happened in the days of Nehemiah.
وَهذَا مَا جَرَى أَيَّامَ نَحَمْيَا ،‏ حِينَ ٱضْطُرَّ ٱللَّاوِيُّونَ أَنْ يُهْمِلُوا خِدْمَتَهُمْ لِكَيْ يَعْمَلُوا فِي حُقُولِهِمْ .‏ ‏