وَإِذْ تَأَذَّنَ رَبُّكُمْ لَئِن شَكَرْتُمْ لَأَزِيدَنَّكُمْ ۖ وَلَئِن كَفَرْتُمْ إِنَّ عَذَابِى لَشَدِيدٌ
Wai th taa thth ana rabbukum lain shakartum laazeedannakum walain kafartum inna AAa tha bee lashadeed un And [remember the time] when your Sustainer made [this promise] known: 'If you are grateful [to Me], I shall most certainly give you more and more;8 but if you are ungrateful, verily, My chastisement will be severe indeed!'"
 - Mohammad Asad
Remember that your Rabb had forewarned: "If you are grateful, I will bestow abundance upon you, but if you are ungrateful (then you should know that) My punishment will be terrible indeed."
 - Muhammad Farooq-i-Azam Malik
And 'remember' when your Lord proclaimed, 'If you are grateful, I will certainly give you more. But if you are ungrateful, surely My punishment is severe.''
 - Mustafa Khattab
And when your Lord proclaimed: If ye give thanks, I will give you more; but if ye are thankless, lo! my punishment is dire.
 - Marmaduke Pickthall
And remember! your Lord caused to be declared (publicly): "If ye are grateful I will add more (favors) unto you; but if ye show ingratitude truly My punishment is terrible indeed." 1879
 - Abdullah Yusuf Ali