Hadithcore
Sahih Muslim, 2041 b
sahih

Anas b. Malik reported that a person invited Allah's Messenger (ﷺ) to a meal. I also went along with him. He brought soup containing pumpkin. Allah's 'messenger (ﷺ) ate that pumpkin with relish. He (Anas) said:

When I saw that I began to place it before him, and did not eat it (myself). Anas said: It was since then that pumpkin was always my favourite (food).

حَدَّثَنَا مُحَمَّدُ بْنُ الْعَلاَءِ أَبُو كُرَيْبٍ، حَدَّثَنَا أَبُو أُسَامَةَ، عَنْ سُلَيْمَانَ بْنِ الْمُغِيرَةِ، عَنْ ثَابِتٍ، عَنْ أَنَسٍ، قَالَ دَعَا رَسُولَ اللَّهِ صلى الله عليه وسلم رَجُلٌ فَانْطَلَقْتُ مَعَهُ فَجِيءَ بِمَرَقَةٍ فِيهَا دُبَّاءٌ فَجَعَلَ رَسُولُ اللَّهِ صلى الله عليه وسلم يَأْكُلُ مِنْ ذَلِكَ الدُّبَّاءِ وَيُعْجِبُهُ - قَالَ - فَلَمَّا رَأَيْتُ ذَلِكَ جَعَلْتُ أُلْقِيهِ إِلَيْهِ وَلاَ أَطْعَمُهُ ‏.‏ قَالَ فَقَالَ أَنَسٌ فَمَا زِلْتُ بَعْدُ يُعْجِبُنِي الدُّبَّاءُ ‏.‏

References2 variants
In-Book Reference
Book 36, Hadith 200
USC-MSA web (English) reference
Book 23, Hadith 5068 (deprecated numbering scheme)