Before entering upon the duties of his office, each attorney at law shall take and subscribe the following oath or affirmation before a person authorized to administer oaths:
"I do solemnly swear (or affirm) that I will support, obey and defend the Constitution of the United States and the Constitution of this Commonwealth and that I will discharge the duties of my office with fidelity, as well to the court as to the client, that I will use no falsehood, nor delay the cause of any person for lucre or malice."
Any person refusing to take the oath or affirmation shall forfeit his office.