This saying is widely ascribed to Qasim son of Imam Hasan Mujtaba (a.s.). It is said that when his beloved uncle, Imam Hussein (a.s.) asked him "My child, my nephew, tell me, how do you regard death and what do you think about getting killed?" He promptly answered: "Death is sweater to me than honey."
This narration has been mentioned in Madinat Ma'ajiz al-Aemmah al-Ithna Ashar wa Dalael al-Hujaj 'alaa al-Bashar, vol.4, pg. 215 and 228 cited originally from al-Hedayatul Kubra authored by Hussein bin Hamdan al-Hazini, pg.43 (manuscript).
Hussein bin Hamdan al-Hazini died in the year 346 A.H. at age 84 of his life (born 260 A.H.). He was buried in the northern part of Halab (a city in Iraq). His tomb known as that of "Al-Shaykh Bāiraq" is well-known and it is visited by the lovers of the Commander of the Faithful.
This book has been printed and published and the above report can be found on page 204 of the same book.
 - Madina Ma'ajiz has been written by Sayed Hashim Bahrani who died in the year 1107 A.H.