Abu Ḥamid bin Abu Bakr Ibraahim (c. 1145 – c. 1221; ابو حامد بن ابوبکر ابراهیم‎), better known by his pen-names Farid ud-Din (فرید الدین) and ʿAṭṭar (عطار, Attar means apothecary), was a Persian poet, theoretician of Sufism, and hagiographer from Nishapur who had an immense and lasting influence on Persian poetry and Sufism.  His works were the inspiration of Rumi and many other mystic poets. `Attar, along with Sanai were two of the greatest influences on Rumi in his Sufi views. Rumi has mentioned both of them with the highest esteem several times in his poetry.

There is not much information available regarding Attar's life. However, all sources confirm that he was from Nishapur, a major city of medieval Khorasan (now located in the northeast of Iran), and he was a poet of the Seljuq period.

According to Edward G. Browne, Attar as well as Rumi and Sana'i, were Sunni.  According to Annemarie Schimmel, the tendency among Shia authors to include leading mystical poets such as Rumi and Attar among their own ranks, became stronger after the introduction of Twelver Shia as the state religion in the Safavid Empire in 1501.

Source: https://en.wikipedia.org/wiki/Attar_of_Nishapur