The Quran

أَينَما تَكونوا يُدرِككُمُ المَوتُ وَلَو كُنتُم في بُروجٍ مُشَيَّدَةٍ ۗ وَإِن تُصِبهُم حَسَنَةٌ يَقولوا هٰذِهِ مِن عِندِ اللَّهِ ۖ وَإِن تُصِبهُم سَيِّئَةٌ يَقولوا هٰذِهِ مِن عِندِكَ ۚ قُل كُلٌّ مِن عِندِ اللَّهِ ۖ فَمالِ هٰؤُلاءِ القَومِ لا يَكادونَ يَفقَهونَ حَديثًا

Muhammad Asad

Wherever you may be, death will overtake you - even though you be in towers raised high. "Yet, when a good thing happens to them, some [people] say, "This is from God," whereas when evil befalls them, they say, "This is from thee [O fellowman]!"¹ Say: "All is from God." What, then, is amiss with these people that they are in no wise near to grasping the truth of what they are told?²

I.e., they do not realize that the evil happening may possibly be a consequence of their own actions or their own wrong choice between several courses open to them, but are prone to attribute it to the failings of others.
Lit., "something [which they are] told" - i.e., a truth which their own reason as well as the teachings of all the prophets should have made obvious to them.