May we then swear religiously by the name of God?
Yes: either when the magistrates demand it of the subjects; or when necessity requires us thereby to confirm a fidelity and truth to the glory of God, and the safety of our neighbour: for such an oath is founded on God's word,1 and therefore was justly used by the saints, both in the Old and New Testament.2
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;3 which honour is due to no creature.4
2 Gen. 21:24; Gen. 31:53, 54; Jos. 9:15, 19; 1 Sam. 24:22; 2 Sam. 3:35; 1 Kin. 1:28-30; Rom. 1:9; 2 Cor. 1:23.