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  

Only Um Hani told us that she had seen the Prophet ﷺ offering the Duha (forenoon prayer). She said, "On the day of the conquest of Mecca, the Prophet ﷺ took a bath in my house and offered eight rakʿat. I never saw him praying such a light prayer but he performed perfect prostration and bowing.  

أَنَّهُ رَأَى النَّبِيَّ ﷺ صَلَّى الضُّحَى غَيْرُ أُمِّ هَانِئٍ ذَكَرَتْ أَنَّ النَّبِيَّ ﷺ يَوْمَ فَتْحِ مَكَّةَ اغْتَسَلَ فِي بَيْتِهَا فَصَلَّى ثَمَانِ رَكَعَاتٍ فَمَا رَأَيْتُهُ صَلَّى صَلاَةً أَخَفَّ مِنْهَا غَيْرَ أَنَّهُ يُتِمُّ الرُّكُوعَ وَالسُّجُودَ  

My friend (the Prophet ﷺ) advised me to do three things and I shall not leave them till I die: (1) to fast three days every month, (2) to offer the Duha prayer, and (3) to offer Witr before sleeping.  

أَوْصَانِي خَلِيلِي بِثَلاَثٍ لاَ أَدَعُهُنَّ حَتَّى أَمُوتَ: (١) صَوْمِ ثَلاَثَةِ أَيَّامٍ مِنْ كُلِّ شَهْرٍ، (٢) وَصَلاَةِ الضُّحَى، (٣) وَنَوْمٍ عَلَى وِتْرٍ.