Mich. Comp. Laws § 51.73: Sheriff; appointments and revocations, form, filing; oaths of office.

Sec. 73.

Every appointment of an under sheriff, or of a deputy sheriff, and every revocation thereof, shall be in writing under the hand of the sheriff, and shall be filed and recorded in the office of the clerk of the county; and every such under sheriff or deputy shall, before he enters upon the duties of his office, take the oath prescribed by the twelfth article of the constitution of this state. But this section shall not extend to any person who may be deputed by any sheriff to do a particular act only.