Here in the printer’s manuscript, Oliver Cowdery initially wrote the verb in the present tense (namely, commandeth). Somewhat later, perhaps when proofing against 𝓞, he crossed out the -eth ending and supralinearly inserted the past-tense ending -ed (the level of the ink flow is somewhat heavier). The past tense is used throughout the larger passage, including a preceding occurrence of commanded and a following one (listed as 1 and 3 below):
Oliver probably wrote the second commanded initially as commandeth because the two preceding present-participial clauses seem to imply the present tense: “having one faith and one baptism / having their hearts knit together in unity and in love one towards another”. The critical text will maintain the use of the past-tense commanded throughout this passage.
Summary: Maintain in Mosiah 18:22 the past-tense commanded, the corrected reading in 𝓟; the surrounding text is also in the past tense.