وَإِذْ تَأَذَّنَ رَبُّكُمْ لَئِن شَكَرْتُمْ لَأَزِيدَنَّكُمْ ۖ وَلَئِن كَفَرْتُمْ إِنَّ عَذَابِى لَشَدِيدٌ
Wa iz ta azzana Rabbukum la'in shakartum la azeedannakum wa la'in kafartum inn'azaabee lashadeed
And remember when your Lord proclaimed: 'If you are grateful, I will surely give you more; but if you deny, my punishment is severe.'