Messenger of Allah ﷺ used to give up a good deed, although he loved to do it, for fear that people might act on it and it might be made compulsory for them. The Prophet ﷺ never prayed the Duha prayer, but I offer it.  

إِنْ كَانَ رَسُولُ اللَّهِ ﷺ لَيَدَعُ الْعَمَلَ وَهْوَ يُحِبُّ أَنْ يَعْمَلَ بِهِ خَشْيَةَ أَنْ يَعْمَلَ بِهِ النَّاسُ فَيُفْرَضَ عَلَيْهِمْ وَمَا سَبَّحَ رَسُولُ اللَّهِ ﷺ سُبْحَةَ الضُّحَى قَطُّ وَإِنِّي لأُسَبِّحُهَا  

I have never seen the Messenger of Allah ﷺ observing the supererogatory prayer of the forenoon, but I observed it. And if the Messenger of Allah ﷺ abandoned any act which he in fact loved to do, it was out of fear that if the people practised it constantly, it might become obligatory for them.  

أَنَّهَا قَالَتْ مَا رَأَيْتُ رَسُولَ اللَّهِ ﷺ يُصَلِّي سُبْحَةَ الضُّحَى قَطُّ وَإِنِّي لأُسَبِّحُهَا وَإِنْ كَانَ رَسُولُ اللَّهِ ﷺ لَيَدَعُ الْعَمَلَ وَهُوَ يُحِبُّ أَنْ يَعْمَلَ بِهِ خَشْيَةَ أَنْ يَعْمَلَ بِهِ النَّاسُ فَيُفْرَضَ عَلَيْهِمْ  

The Messenger of Allah ﷺ never offered prayer in the forenoon, but I offer it. The Messenger of Allah ﷺ would give up an action, though he liked it to do, lest the people should continue it and it is prescribed for them.  

عَنْ عَائِشَةَ زَوْجِ النَّبِيِّ ﷺ أَنَّهَا قَالَتْ مَا سَبَّحَ رَسُولُ اللَّهِ ﷺ سُبْحَةَ الضُّحَى قَطُّ وَإِنِّي لأُسَبِّحُهَا وَإِنْ كَانَ رَسُولُ اللَّهِ ﷺ لَيَدَعُ الْعَمَلَ وَهُوَ يُحِبُّ أَنْ يَعْمَلَ بِهِ خَشْيَةَ أَنْ يَعْمَلَ بِهِ النَّاسُ فَيُفْرَضَ عَلَيْهِمْ  

Yahya related to me from Malik from Ibn Shihab from Urwa ibn az- Zubayr that A'isha, the wife of the Prophet ﷺ said, "I never once saw the Messenger of Allah ﷺ doing the voluntary prayer of duha, but I myself do it. Sometimes the Messenger of Allah ﷺ would refrain from a practice that he loved to do, fearing that people would do the same and it would become fard for them ."  

عَنْ عَائِشَةَ زَوْجِ النَّبِيِّ ﷺ أَنَّهَا قَالَتْ مَا رَأَيْتُ رَسُولَ اللَّهِ ﷺ يُصَلِّي سُبْحَةَ الضُّحَى قَطُّ وَإِنِّي لأُسَبِّحُهَا وَإِنْ كَانَ رَسُولُ اللَّهِ ﷺ لَيَدَعُ الْعَمَلَ وَهُوَ يُحِبُّ أَنْ يَعْمَلَهُ خَشْيَةَ أَنْ يَعْمَلَ بِهِ النَّاسُ فَيُفْرَضَ عَلَيْهِمْ  

The Messenger of Allah ﷺ never offered prayer in the forenoon, but I offer it. The Messenger of Allah ﷺ would give up an action, though he liked it to do, lest the people should continue it and it is prescribed for them. (Using translation from Abū Dāʾūd 1293)  

عَنْ عَائِشَةَ زَوْجِ النَّبِيِّ ﷺ أَنَّهَا قَالَتْ مَا صَلَّى رَسُولُ اللهِ ﷺ سُبْحَةَ الضُّحَى قَطُّ وَإِنِّي لَأُسَبِّحُهَا وَإِنْ كَانَ رَسُولُ اللهِ ﷺ لَيَدَعُ الْعَمَلَ وَهُوَ يُحِبُّ أَنْ يَعْمَلَ بِهِ خَشْيَةَ أَنْ يَعْمَلَ بِهِ النَّاسُ فَيُفْرَضَ عَلَيْهِمْ  

I have never seen the Messenger of Allah ﷺ observing the supererogatory prayer of the forenoon, but I observed it. And if the Messenger of Allah ﷺ abandoned any act which he in fact loved to do, it was out of fear that if the people practised it constantly, it might become obligatory for them. (Using translation from Muslim 718)  

«مَا رَأَيْتُ رَسُولَ اللهِ ﷺ يُصَلِّي سُبْحَةَ الضُّحَى قَطُّ وَإِنِّي لَأُسَبِّحُهَا وَإِنْ كَانَ رَسُولُ اللهِ ﷺ لَيَدَعَ الْعَمَلَ وَهُوَ يُحِبُّ أَنْ يَعْمَلَهُ خَشْيَةَ أَنْ يَعْمَلَ بِهِ النَّاسُ فَيُفْرَضُ عَلَيْهِمْ»