Imam al-Baqir (AS) said:

لَمّا خَلَقَ اللَّهُ العَقلَ قالَ لَهُ: أقبِلْ فَأقبَلَ، ثُمَّ قالَ لَهُ: أدبِرْ ، فقالَ: وعِزَّتي وجَلالي ما خَلَقتُ خَلقاً أحسَنَ مِنكَ‏، إيّاكَ آمُرُ وإيّاكَ أنهى‏، وإيّاكَ اُثيبُ وإيّاكَ اُعاقِبُ.

‘When Allah created the intellect He said to it, ‘Come forward’ so it came forward, then commanded it, ‘Go back’ and it went back. Then He said to it, ‘By my Honour and Exaltedness, I have not created anything better than you. It is you that I command, and you that I prohibit from things, and you that I punish and you that I reward.’

al-Kafi, v. 1, p. 26, no. 26