Is it Sa'id ibn al-Musayyab with a fatha over the ya or a kasra?

Saeed ibn al-Musayyab was the Sheikh of Islam and the jurist of Madinah, one of the most distinguished Tabi'een (Successors). He was born during the caliphate of Umar. He heard from prominent Companions such as Umar, Uthman, Aisha, and Abu Hurairah. He was vast in knowledge, strong in his faith, and a speaker of truth. The Companions and the Tabi'een bore witness to his knowledge and religious devotion. He passed away in the year 94 AH. His father's name is sometimes pronounced with an open "ya" (al-Musayyab) and sometimes with a broken "ya" (al-Musayyib), and there is no difference resulting from this.