The Prophet ﷺ said, "No one who enters Paradise would ever wish to leave it, even if he were given everything on earth, except for the martyr. He wishes to return and be killed again because of the honor he sees," or words to that effect.
حدثنا عمرو بن الهيثم أبو قطن حدثنا شعبة عن قتادة
عن النبي ﷺ قال ما من أحد يدخل الجنة يحب أن يخرج منها وإن له ما على الأرض من شيء غير الشهيد يحب أن يخرج فيقتل لما يرى من الكرامة أو معناه
Its isnad is sahih. The hadith was narrated by Bukhari 4/26 in jihad, chapter on the mujahid wishing to return, Muslim 3/1498 no. 1877 in leadership, chapter on the merit of jihad, Tirmidhi 4/177 no. 1643 similarly, Nasai 6/33 no. 3153, and Darimi 2/271 no. 2409.