XXXVIII. Of Christian men’s goods which are not common
The riches and goods of Christians are not common, as touching the right, title, and possession of the same, as certain Anabaptists do falsely boast; notwithstanding every man ought of such things as he possesseth liberally to give alms to the poor, according to his ability.
XXXIX. Of a Christian man’s Oath
As we confess that vain and rash swearing is forbidden Christian men by our Lord Jesus Christ, so we judge that Christian religion doth not prohibit but that a man may swear when the magistrate requireth in a cause of faith and charity, so it be done according to the Prophet's teaching in justice, judgement, and truth.
Thus concludes the Thirty-Nine Articles. Both of these last two articles are aimed against certain Anabaptists (for example, see here). From our perspective today, things such as oaths do not seem to merit something as weighty as confessional status. Why is it so important that it must be placed into the official statement of faith?
The answer is fairly simple - such things were so debated because the very nature of human society was at stake. You might compare it to debates about health care today. Everyone in the debate recognizes that more than health care per se is at stake; consequently, it has become a focal point of contention for competing visions of human society. The same kind of thing was true about the debates over oaths in the days of the Reformation.