What is the ruling on saying "even Jibreel (peace be upon him) cannot do that" in the context of negating the ability to meticulously monitor borders, and is repentance required for it?

Denial of knowledge and power concerning Gabriel, peace be upon him, in some matters, especially if not intended as a disparagement, does not constitute disbelief. Gabriel possesses great power and ability in what Allah has commanded him and permitted him to do, for he is "mighty in power" and strong in executing commands, delivering revelation, and preventing its stealth by devils. However, he is one of Allah's creatures and is only capable of what Allah has enabled him to do, and only knows what Allah has informed him of.