Or HaChaim on Deuteronomy 1:13/אור החיים על דברים א׳:י״ג

1 הבו לכם אנשים חכמים, "get for yourselves wise and understanding men, etc." He advisedly used the word "for yourselves" before mentioning that they should be from their respective tribes as the fact that the judges would be selected from within the respective tribes would result in many beneficial effects for the members of these tribes. Please compare what I have written in Parshat Pinchas on Numbers 27,16 "may the Lord of all spirits appoint a man over the congregation."

2ואשימם בראשיכם, "and I will place them as heads over you." Moses means that although he told the people that the appointment of these judges would be for their benefit, i.e. that they themselves would be allowed to select these judges, the fact remained that these judges would exert their authority over the people, if necessary backed up by means of enforcing same.