As was already shown by Bertels, the way Nizāmī made use of his sources was arbitrary, in the sense that he did not refrain from changing his sources to accord with his own ideas. However, when it comes to the goals that Nizāmī pursued by introducing these alterations, there is nothing at all arbitrary. Where Nizāmīaltered his sources, it was to illustrate his humanistic ideas.

In considering Nizāmī's sources, one has to make a division between two different types: first, the general source from which a basic idea or overall plot stems, and second, sources employed only for certain particular events, or inserted stories, etc. Thus the general idea for Makhzan al-asrār, a didactic epos dealing with twenty moral topics each illustrated by one little story, came from Sanā’ī's Hadīqat al-haqīqa, as Nizāmī himself suggests in the beginning of this epos by his reference to Sanā’ī, without however naming the Hadīqat expressly. The strict structural device, however, was apparently his own contribution. Three of the four following epics drew their subject matter from the Shāhnāma, namely Khusraw and Shīrīn, Haft Paikar and Iskandarnāma. Lailā and Majnūn was inspired by Arabic sources, probably the long chapter in the Kitāb al-aghānī. Yet, nowhere did Nizāmī restrict himself to just one source. The mere intention to surpass his models, to outdo his predecessors, as he often claims to have done, implied the necessity of using more than just the one source from which the initial impulse had come.