"When the messengers came to them from before them and from behind them," meaning: they warned them of the punishment of this world and the punishment of the Hereafter.
"They said: Had our Lord willed, He would have sent down angels," meaning: they would inform us that you are the messengers of God; every people said this to their messenger.
﴿إِذْ جَاءَتْهُمُ الرُّسُلُ مِنْ بَيْنِ أَيْديهم وَمن خَلفهم﴾ أَي: أنذروهم عَذَاب الدُّنْيَا وَعَذَاب الْآخِرَة.
﴿قَالُوا لَوْ شَاءَ رَبُّنَا لأنزل مَلَائِكَة﴾ أَي: يخبروننا أَنكُمْ رسل اللَّه؛ يَقُوله كل قوم لرسولهم.