“… and who fulfil their covenant when they make it…” [al-Baqarah 2:177]

“Among the believers are men who have been true to their covenant with Allaah [i.e., they have gone out for jihad (holy fighting), and showed not their backs to the disbelievers], of them some have fulfilled their obligations (i.e., have been martyred), and some of them are still waiting, but they have never changed [i.e., they never proved treacherous to their covenant which they concluded with Allaah] in the least.” [al-Ahzaab 33:23]