Before various traditions coalesced around Muhammad as the core prophetic figurehead, 7th c formulae invoked Allāh as Lord of Mūsa, ‘Isà, & other prophets.
"That Allah may forgive thee [Muhammad] of thy sin that which is past and that which is to come." Q 48:2
Crossroads to Islam: The Origins of the Arab Religion and the Arab State
By Yehuda D. Nevo, Judith Koren
books.google.com/books?id=_pT0K…