It is narrated from Sayyiduna Jundub bin Abdullah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever is able to ensure that not even a palmful of blood comes between him and Paradise, blood which he sheds as though he were slaughtering a chicken, (let him do so): every time he advances towards one of the gates of Paradise, that blood will come between him and it. Whoever of you is able to put nothing into his stomach except what is pure, let him do so, for the first part of a person to rot is his stomach."
Hadith Referenceالمعجم الكبير للطبراني / باب الجيم / 1649