The presentation is going to deal with two palimpsests preserved in the collection of the monastery of St. Catherine on Mount Sinai, namely Arabic 514 and Arabic 588 that were included in the ‘Sinai Palimpsests Project’ (directed by M. Phelps and C. Rapp). Although the two palimpsests under consideration were not totally unknown to scholars, none of them was studied systematically with an attempt to identify the manuscripts and texts that were reused for their production. Two Arabic manuscripts have much in common. Both are palimpsests throughout and both were made out of different manuscripts, mostly in Syriac language. In my talk, I will introduce the Syriac manuscripts that were reused with a particular attention to the apocryphal texts that have been identified.