May we swear an oath reverently by the name of God?
Yes, either when the authorities require it of citizens, or when necessity requires us thereby to confirm faithfulness and truth to the glory of God and the safety of our neighbour, for such an oath is founded on God's word and therefore was justly used by the saints both in the Old and New Testament.
May we also swear by saints or any other creatures?
No, for a lawful oath is calling upon God as the only one who knows the heart, that He will bear witness to the truth and punish me if I swear falsely, which honour is due to no creature.