Abdullah bin Mubarak عبد الله بن المبارك · The Book Of Faith and its Signs

The Prophet commanded him to call out on the days of At-Tashriq that no one would enter Paradise except a believer, and that these were the days of eating and drinking.

"The Messenger of Allah said: 'Allah, the Mighty and Sublime, has guaranteed to the one who goes out in His cause, 'and he does not go out for any other purpose except Jihad in My cause and faith in Me, believing in My Messengers, but he is guaranteed that I will admit him to Paradise or I will send him back to his dwelling from which he set out, having acquired whatever he acquired of reward or spoils of war.'"