Tafsir of Az-Zukhruf 43:50

Invoke your Lord for us according to what He has made a pact with you. Verily, We shall guide ourselves.'' But when We removed the torment from them, behold, they broke their covenant. On each occasion, they promised Musa that if the torment was lifted from them, they would believe in him and let the Children of Israel go with him, but on each occasion they went back on their word. This is like the Ayat:

فٲرسلنا عليهم الطوفان والجراد والقمل والضفادع والدم ءايت مفصﻼت فاستكبروا وكانوا قوما مجرمين

ولما وقع عليهم الرجز قالوا يموسى ادع لنا ربك بما عهد عندك لين كشفت عنا الرجز لنومنن لك ولنرسلن معك بنى إسرءيل

فلما كشفنا عنهم الرجز إلى أجل هم بلغوه إذا هم ينكثون

So We sent on them: the flood, the locusts, the Qummal, the frogs, and the blood; manifest signs, yet they remained arrogant, and they were of those people who were criminals. And when the punishment struck them, they said: "O Musa! Invoke your Lord for us because of His promise to you. If you remove the punishment from us, we indeed shall believe in you, and we shall let the Children of Israel go with you.'' But when We removed the punishment from them to a fixed term, which they had to reach, behold! they broke their word! (7:133-135)