Oaths in Scots have been used for a long time. The following examples are taken from The Records of the Parliaments of Scotland to 1707. 

1587

And we solempnatlie swear, in presence of our saidis thrie estaitis, be oure grite aith presentlie gevin at this our first parliament haldin efter oure perfite aige of xxj yeiris compleit, and as we wer oblist to have done incais we had bene of perfite aige at or coronatioun, that we sall faithfullie observe and keip the statute and act of parliament maid in the dayes of oure maist noble predicessour King James the Secund, anent the keping and retening of the landis, lordschipis and baronies annext to the patrimonie of the croun in all pointis and claussis thairof.

1617

You sall sweare that you sall faithfullie and trewlie discharge your office of constabularie within the parochin off etc.

1689

I, A. B. doe sincerly promise and swear that I will be faithfull and bear true alledgiance to their majesties King Wiliam and Queen Mary, so help me God.