In Singapore you don't have to swear an oath in court if you are of certain religions. Instead you affirm that you're speaking the truth:
Circumstances under which affirmation may be made 16. Any person who —(a) is a Hindu or Muslim or of some other religion according to which oaths are not of binding force; or(b) has a conscientious objection to taking an oath,and who is required to take an oath of office or judicial oath under any written law may, instead of taking the oaths referred to in section 15 (1) or (2), as the case may be, make an affirmation in the form of those oaths, substituting the words “solemnly, sincerely and truly declare and affirm” for the word “swear” and omitting the words “So help me God”.
I'm curious if that means oaths in British English have an implied religious meaning? It seems to be the case that you swear to God usually, but an oath in itself is irreligious, no?