Surah Al-Kahf, ayah 23

وَلَا تَقُولَنَّ لِشَاْيۡءٍ إِنِّي فَاعِلٞ ذَٰلِكَ غَدًا ٢٣

Walā taqūlanna lishay'in innī fā'ilun dhālika ghadā

And never say of anything, "Indeed, I will do that tomorrow,"