Adam Clarke on 2 Thessalonians 3:9

Not because we have not power - We have the power, εξουσιαν, the right, to be maintained by those in whose behalf we labor. The laborer is worthy of his hire, is a maxim universally acknowledged and respected; and they who preach the Gospel should live by the Gospel: the apostle did not claim his privilege, but labored for his own support, that he might be an example to those whom he found otherwise disposed, and that he might spare the poor. See 1Cor 9:1, etc.