Abbas Di Palma, Shaykh Abbas Di Palma holds a BA and an MA degree in Islamic Studies, and certifications from the Language Institute of Damascus University. He has also studied traditional Islamic sciences in... Answer updated 3 years ago

as salam alaikum

the divine commands for 'ibadaat are "tawqifiyyah" meaning it is not permissible to add anything on them that has not been clearly prescribed by Allah Almighty. Since al-Shahadah al-Thalithah during salat has not been transmitted through authentic or widely transmitted reports, and actually the authentic reports prove otherwise, it cannot be considered neither "wajib" nor "sunnah" or "mustahab".

With prayers for your success.