To what does the phrase “هَٰذَا مِنْ عَمَلِ الشَّيْطَانِ” refer in the story of Moses and the Egyptian?

عَنْ عَلِيِّ بْنِ مُحَمَّدِ بْنِ الْجَهْمِ، قَالَ: حَضَرْتُ مَجْلِسَ الْمَأْمُونِ، وَ عِنْدَهُ الرِّضَا عَلِيُّ بْنُ مُوسَى (عَلَيْهِمَا السَّلَامُ)- وَ ذَكَرَ حَدِيثَ عِصْمَةِ الْأَنْبِيَاءِ (عَلَيْهِمُ السَّلَامُ)، وَ قَدْ ذَكَرْنَا مِنْهُ غَيْرَ مَرَّةٍ- فَكَانَ فِيمَا سَأَلَ الْمَأْمُونُ الرِّضَا (عَلَيْهِ السَّلَامُ) أَنْ قَالَ لَهُ: أَخْبِرْنِي عَنْ قَوْلِ اللَّهِ عَزَّ وَ جَلَّ: فَوَكَزَهُ Moses struck him and brought him down عَلَيْهِ قالَ هذا مِنْ عَمَلِ الشَّيْطانِ.
قَالَ الرِّضَا (عَلَيْهِ السَّلَامُ): «إِنَّ مُوسَى (عَلَيْهِ السَّلَامُ) دَخَلَ مَدِينَةً مِنْ مَدَائِنِ فِرْعَوْنَ عَلَى حِينِ غَفْلَةٍ مِنَ أَهْلِهَا، وَ ذَلِكَ بَيْنَ الْمَغْرِبِ وَ الْعِشَاءِ، فَوَجَدَ فِيهَا رَجُلَيْنِ يَقْتَتِلَانِ: هَذَا مِنْ شِيعَتِهِ، وَ هَذَا مِنْ عَدُوِّهِ، فَاسْتَغَاثَهُ الَّذِي مِنْ شِيعَتِهِ عَلَى الَّذِي مِنْ عَدُوِّهِ، فَقَضَى مُوسَى (عَلَيْهِ السَّلَامُ) عَلَى الْعَدُوِّ بِحُكْمِ اللَّهِ تَعَالَى، فَوَكَزَهُ فَمَاتَ، قَالَ: هذا مِنْ عَمَلِ الشَّيْطانِ يَعْنِي الِاقْتِتَالَ الَّذِي كَانَ وَقَعَ بَيْنَ الرِّجْلَيْنِ، لَا مَا فَعَلَهُ مُوسَى (عَلَيْهِ السَّلَامُ) مِنْ قَتْلِهِ، إِنَّهُ يَعْنِي Satan عَدُوٌّ مُضِلٌّ مُبِينٌ».
قَالَ الْمَأْمُونُ: فَمَا مَعْنَى قَوْلِ مُوسَى (عَلَيْهِ السَّلَامُ): رَبِّ إِنِّي ظَلَمْتُ نَفْسِي فَاغْفِرْ لِي؟
قَالَ: «يَقُولُ: إِنِّي وَضَعْتُ نَفْسِي غَيْرَ مَوْضِعِهَا بِدُخُولِ هَذِهِ الْمَدِينَةِ، فَاغْفِرْ لِي، أَيْ اسْتُرْنِي مِنْ أَعْدَائِكَ لِئَلَّا يَظْفَرُوا بِي فَيَقْتُلُونِي فَغَفَرَ لَهُ إِنَّهُ هُوَ الْغَفُورُ الرَّحِيمُ، قَالَ مُوسَى (عَلَيْهِ السَّلَامُ): رَبِّ بِما أَنْعَمْتَ عَلَيَّ مِنَ الْقُوَّةِ حَتَّى قَتَلْتُ رَجُلًا بِوَكْزَةٍ فَلَنْ أَكُونَ ظَهِيراً لِلْمُجْرِمِينَ بَلْ أُجَاهِدُ فِي سَبِيلِكَ بِهَذِهِ الْقُوَّةِ حَتَّى تَرْضَى.
فَأَصْبَحَ مُوسَى (عَلَيْهِ السَّلَامُ) فِي الْمَدِينَةِ خائِفاً يَتَرَقَّبُ فَإِذَا الَّذِي اسْتَنْصَرَهُ بِالْأَمْسِ يَسْتَصْرِخُهُ، قَالَ لَهُ مُوسَى: إِنَّكَ لَغَوِيٌّ مُبِينٌ، قَاتَلْتَ رَجُلًا بِالْأَمْسِ، وَ تُقَاتِلُ هَذَا الْيَوْمَ؟ لَأُؤَدِّبَنَّكَ ، وَ أَرَادَ أَنْ يَبْطِشَ بِهِ، فَلَمَّا أَرَادَ أَنْ يَبْطِشَ بِالَّذِي هُوَ عَدُوٌّ لَهُمَا، وَ هُوَ مِنْ شِيعَتِهِ، قَالَ: يَا مُوسَى: أَ تُرِيدُ أَنْ تَقْتُلَنِي كَما قَتَلْتَ نَفْساً بِالْأَمْسِ إِنْ تُرِيدُ إِلَّا أَنْ تَكُونَ جَبَّاراً فِي الْأَرْضِ وَ ما تُرِيدُ أَنْ تَكُونَ مِنَ الْمُصْلِحِينَ».
قَالَ الْمَأْمُونُ: جَزَاكَ اللَّهُ عَنْ أَنْبِيَائِهِ خَيْراً، يَا أَبَا الْحَسَنِ.
Al-Burhān fī Tafsīr al-Qurʾān, vol. 4, p. 260

ʿAlī ibn Muḥammad ibn Jahm relates: I was present at a gathering of al-Maʾmūn, where al-Riḍā ʿAlī ibn Mūsā (peace be upon them both) was also present. The Imam was discussing the infallibility of the Prophets (peace be upon them), a subject we have recounted many times. Among the questions al-Maʾmūn put to Imam al-Riḍā (peace be upon him) was this: “Explain to me the meaning of the words of God, Mighty and Glorious: ‘Moses struck him and brought him down. He said: This is the work of Satan.’”

Imam al-Riḍā (peace be upon him) replied: “Moses (peace be upon him) entered one of the cities of Pharaoh’s people at a time when its inhabitants were unaware—between sunset and nightfall. There he found two men fighting, one of them a follower of his and the other an enemy. The one who followed him called on him for help against his enemy. Moses (peace be upon him) therefore judged against the enemy in accordance with God’s command, struck him, and he died. Moses said, ‘This is the work of Satan’—meaning the fight between the two men, not his own act in killing the man. ‘He’ refers to Satan, the manifest, misleading enemy.”

Al-Maʾmūn asked: “Then what is the meaning of Moses’ words: ‘My Lord, I have wronged myself, so forgive me’?”

The Imam replied: “He meant: ‘By entering this city, I put myself in a dangerous and unsuitable position, so forgive me’—that is, conceal me from Your enemies, lest they overpower and kill me. So God forgave him; indeed, He is the All-Forgiving, the Most Merciful. Moses (peace be upon him) said: ‘My Lord, for the strength You have bestowed upon me—for I killed a man with a single blow—I will never support sinners. Rather, I will use this strength to strive in Your cause until You are pleased with me.’”

“Moses, peace be upon him, was in the city the following morning, fearful and watchful, waiting to see what might happen, when suddenly the very man who had asked him for help the day before called out to him again. Moses said to him, ‘You are clearly in the wrong! Yesterday you killed a man, and today you are fighting this one too? I will certainly teach you a lesson!’ And he meant to strike him. But when he went to strike someone who was an enemy to them both—and who belonged to his own people—the man said, ‘Moses! Do you intend to kill me as you killed someone yesterday? You want nothing but to become a tyrant in this land; you do not want to be one of those who set things right!’”

Al-Ma’mun said, “May God reward you well for your words concerning His prophets, O Abu al-Hasan!”