Al-Qasim bin Muhammad says: I was with Ibn Umar (may Allah be pleased with them both) when a man came to him and said: I intend to travel. So Abdullah bin Umar (may Allah be pleased with them both) said: Wait, so that I may bid you farewell as the Messenger of Allah (peace and blessings be upon him) used to bid us farewell: '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 / 10312