Okla. Stat. tit. 58, § 161

Before letters testamentary or of administration are issued to the executor or administrator, he must take and subscribe an oath, before some officer authorized to administer oaths, that he will perform, according to law, the duties of executor or administrator, which oath must be attached to the letters. All letters testamentary and of administration issued to, and all bonds executed by executors or administrators, with the affidavits and certificates thereon must be forthwith recorded by the judge in books to be kept by him in his office for that purpose.