The Quran

ذٰلِكَ بِأَنَّهُ كانَت تَأتيهِم رُسُلُهُم بِالبَيِّناتِ فَقالوا أَبَشَرٌ يَهدونَنا فَكَفَروا وَتَوَلَّوا ۚ وَاستَغنَى اللَّهُ ۚ وَاللَّهُ غَنِيٌّ حَميدٌ

Muhammad Asad

this, because time and again therecame unto them their apostles¹ with all evidence of the truth, but they [always] replied, "Shall mere mortal men be our guides?"² And so they. denied the truth and turned away. But God was not in need [of them]: for God is self-sufficient, ever to be praised.

I.e., apostles from their own midst, entrusted with divine messages specifically meant for them. The expression "time and again" is conditioned by the phrase kanat ta'atihim which implies repetition and duration.
Lit., "guide us". This negative response is characteristic of people who, in result of their own estrangement from all moral standards, are instinctively, and deeply, distrustful of all things human and cannot, therefore, accept the idea that a divine message could manifest itself through mere human beings that have nothing "supernatural" about them.