Reference: Siyar A’laam an-Nubalaa. – Volume 14, Page 274
Haaroon ibn ‘Abdil-‘Azeez said:
Abu Ja’far at-Tabaree said: I made istikhaarah to Allaah for three years and asked him for assistance for that which I had made the intention to compile the tafseer before I began, and so he assisted me.