Is an oath prescribed when claiming financial dues belonging to God, such as Zakat due from a tax collector (Sa'i)?

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In cases of financial rights due to God, such as a tax collector claiming Zakat from the owner of wealth, asserting that a full year has passed and the requisite threshold (Nisab) has been met, Ahmad stated that the word of the wealth owner is accepted without an oath, and people are not sworn regarding their charitable donations. The rationale is that this is a right of God, resembling a fixed punishment, and it is an act of worship, so no oath is prescribed, similar to prayer.