Hadithcore
Mishkat al-Masabih, 4217

Anas said God’s messenger liked what was at the bottom of the pot.* *<i>Mirqat</i>, iv, 381 has quite a long discussion of the meaning of <i>thufl</i>. It means 'dregs', or 'what sinks to the bottom'. The preference for the meaning in the translation above is said to "be either because what is in the bottom of the pot is cooked longer and so is better than the rest, or because the Prophet (ﷺ) liked others to be served first. It is also suggested that here <i>thufl</i> means <i>tharid</i>. Tirmidhi and Baihaqi, in <i>Shu'ab al-iman</i>, transmitted it.

وَعَنْ أَنَسٍ قَالَ: كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يُعْجِبُهُ الثُّفْلُ. رَوَاهُ التِّرْمِذِيُّ وَالْبَيْهَقِيُّ فِي شعب الْإِيمَان

References1 variant
In-Book Reference
Book 21, Hadith 54