A Cornerstone of the correct Islaamic 'Aqeedah, the correct understanding pre-ordainment from Allaah.
 

“Indeed, We have created all things with Qadr.” [Sooratul-Qamar 54:49]

“Did we not create you with a fluid of no value? Then We placed it in a place of safety (womb), for a known period (determined by gestation)? So We did measure, and We are the best to measure.”  [Sooratul-Mursalat 77:20-23]

“He has created everything, and has measured it exactly according to its due measure.” [Sooratul-Furqaan 25:2]

From Taawoos who said, ‘I found some Companions of the Messenger of Allaah (sallallaahu ’alayhi wa sallam) saying, ‘Everything is by Qadr (measure).’ And he further said, “I heard ’Abdullaah Ibn ’Umar - radiyallaahu ’anhu - as saying, ‘There is a measure for everything - even for incapacity and capability.” [Related by Muslim (no.6419)]