Appears 6 times in the Quran.
5:66 وَلَوْ أَنَّهُمْ أَقَامُوا۟ ٱلتَّوْرَىٰةَ وَٱلْإِنجِيلَ وَمَآ أُنزِلَ إِلَيْهِم مِّن رَّبِّهِمْ لَأَكَلُوا۟ مِن فَوْقِهِمْ وَمِن تَحْتِ أَرْجُلِهِم مِّنْهُمْ أُمَّةٌ مُّقْتَصِدَةٌ وَكَثِيرٌ مِّنْهُمْ سَآءَ مَا يَعْمَلُونَ
And if they had kept up the Taurat and the Injeel and that which was revealed to them from their Lord, they would certainly have eaten from above them and from beneath their feet there is a party of them keeping to the moderate course, and (as for) most of them, evil is that which they do
9:42 لَوْ كَانَ عَرَضًا قَرِيبًا وَسَفَرًا قَاصِدًا لَّٱتَّبَعُوكَ وَلَٰكِنۢ بَعُدَتْ عَلَيْهِمُ ٱلشُّقَّةُ وَسَيَحْلِفُونَ بِٱللَّهِ لَوِ ٱسْتَطَعْنَا لَخَرَجْنَا مَعَكُمْ يُهْلِكُونَ أَنفُسَهُمْ وَٱللَّهُ يَعْلَمُ إِنَّهُمْ لَكَٰذِبُونَ
Had it been a near advantage and a short journey, they would certainly have followed you, but the tedious journey was too long for them; and they swear by Allah: If we had been able, we would certainly have gone forth with you; they cause their own souls to perish, and Allah knows that they are most surely
And upon Allah it rests to show the right way, and there are some deviating (ways); and if He please He would certainly guide you all aright.
And pursue the right course in your going about and lower your voice; surely the most hateful of voices is braying of the asses.
31:32 وَإِذَا غَشِيَهُم مَّوْجٌ كَٱلظُّلَلِ دَعَوُا۟ ٱللَّهَ مُخْلِصِينَ لَهُ ٱلدِّينَ فَلَمَّا نَجَّىٰهُمْ إِلَى ٱلْبَرِّ فَمِنْهُم مُّقْتَصِدٌ وَمَا يَجْحَدُ بِـَٔايَٰتِنَآ إِلَّا كُلُّ خَتَّارٍ كَفُورٍ
And when a wave like mountains covers them they call upon Allah, being sincere to Him in obedience, but when He brings them safe to the land, some of them follow the middle course; and none denies Our signs but every perfidious, ungrateful one.
35:32 ثُمَّ أَوْرَثْنَا ٱلْكِتَٰبَ ٱلَّذِينَ ٱصْطَفَيْنَا مِنْ عِبَادِنَا فَمِنْهُمْ ظَالِمٌ لِّنَفْسِهِۦ وَمِنْهُم مُّقْتَصِدٌ وَمِنْهُمْ سَابِقٌۢ بِٱلْخَيْرَٰتِ بِإِذْنِ ٱللَّهِ ذَٰلِكَ هُوَ ٱلْفَضْلُ ٱلْكَبِيرُ
Then We gave the Book for an inheritance to those whom We chose from among Our servants; but of them is he who makes his soul to suffer a loss, and of them is he who takes a middle course, and of them is he who is foremost in deeds of goodness by Allah's permission; this is the great excellence.