"And I will grant them respite," meaning: I will prolong their time and grant them a delay until the time arrives in which I shall punish them. "Indeed, My plan is firm," meaning: severe. And His plan (kayd) refers to His seizing them with punishment.
﴿وأملي لَهُم﴾ أَيْ: أُطِيلُ لَهُمْ وَأُمْهِلُهُمْ؛ حَتَّى يَبْلُغَ الْوَقْتُ الَّذِي يُعَذِّبُهُمْ فِيهِ ﴿إِن كيدي متين﴾ شَدِيدٌ، وَكَيْدُهُ: أَخْذُهُ إِيَّاهُمْ بِالْعَذَابِ
