Tafsir of Al-Waqi'ah 56:87

ترجعونها

Then why do you not -- if you are not Madinin -- return the soul, means, `Will you not return this soul, that has reached the throat, to its body as it used to be, if you are exempt from the reckoning and recompense?' Sa`id bin Jubayr and Al-Hasan Al-Basri said,

فلوﻻ إن كنتم غير مدينين

(Then why do you not -- if you are not Madinin. ..), "If you do not believe that you will be reckoned, recompensed, resurrected and punished, then why do you not return this soul to its body'' Mujahid said that,

غير مدينين

(...if you are not Madinin), means, "if you are not certain.''

إن كنتم صادقين

if you are truthful?