Sayyiduna Fadalah bin Ubayd (may Allah be pleased with him) said: I heard the Messenger of Allah (peace and blessings be upon him) say: "I give a guarantee, and the guarantor is the one who takes responsibility, for the one who believes in me, accepts Islam and emigrates: for him are the glad tidings of the outer part of Paradise."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحوالة / 11393