Iranian scholars like Allame Ghazvini, Foruzanfar, Khazaeli, among others, have attempted to look for the main motifs of Sa'di's ideas within the old Arabic poetry. In a detailed study, Hossein-ali Mahfuz claims that the main themes of sa'di thought should be sought in the poetry of Arab poets like Motanabbi. It is understood here that the role of the Iranian ancient culture and literature has been ignored. In the meantime, defenders of Sa'di   have tried to account for the claim mentioned above by appealing to factors like the accidental occurrence of a thought to two different poets unknown to one another, competition at composing a single theme, and by mentioning humane and lofty intentions in Sa'di's texts. Adopting a different approach, the present article attempts to go further back beyond the Abbasids to the Old Iranian culture and literature in the quest for the origins of Sa'di's thought. It will investigate thirty such texts not mentioned in the studies available. These are presented as samples, to demonstrate that our researchers, instead of looking into old Arabic texts, should search Sa'di's thoughts in the ancient Iranian culture.