Assalam o 'alaykum,

Imam Shah Waliullah Dahlawi (may Allah have mercy on him) is of the view that all the Heavenly Books revealed before the Qur'an were revealed after the type of Divine Tradition (Hadith Qudsi), which contained not only the results of the spiritual experiences of those prophets, but an account of their sayings and doings as well. The learned among the followers of that religion were collecting the Divine Book on the strength of their individual reasoning, and the individual reasoning does not always lead to the right conclusion. He says that these books not only had the words and and meanings which the Prophet received directly, but also had a blend of their disciples' individual reasoning.