6. Every person to whom a certificate of naturalization has been granted shall, within thirty days from the date of the grant thereof, take and subscribe the following oath, namely:- "I, A. B., of do hereby swear(or affirm) that I will be faithful and bear true allegiance to ¹[the Constitution of the People's Republic of Bangladesh]: Provided that the Government may extend the time allowed under this section in any case in which it is satisfied that failure to take and subscribe the oath within that time was due to sufficient cause.