Adam Clarke on Joshua 24:15

Choose you this day whom ye will serve - Joshua well knew that all service that was not free and voluntary could be only deceit and hypocrisy, and that God loveth a cheerful giver. He therefore calls upon the people to make their choice, for God himself would not force them - they must serve him with all their heart if they served him at all. As for himself and family, he shows them that their choice was already fixed, for they had taken Jehovah for their portion.