Yahya bin Isma'il bin Jarir narrates from Qaza'ah that Sayyiduna Ibn Umar (may Allah be pleased with them both) sent me on an errand; he took hold of my hand and said: I will bid you farewell as the Messenger of Allah (peace and blessings be upon him) bade me farewell when he sent me on an errand of his, and he said: 'Astawdi'u Allaha dinaka wa amanataka wa khawatima amalik' (I entrust to Allah your religion, your trust and the final outcomes of your deeds.)
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 10311