It is narrated from Sayyiduna Sinan bin Salamah bin Muhabbiq Abu Turayf al-Hudhali (may Allah be pleased with him) that a man from among the Muhajirun gave a large piece of his land in charity to his mother. Then she died, and she had no heir other than him. So he came to the Prophet (peace and blessings be upon him) and said: "My mother, so-and-so, was the dearest of people to me and the most honoured by me, and I had given a large piece of my land in charity to her. Then she died, and she has no heir other than me. So what do you command me to do with it?" He (peace and blessings be upon him) said: "Allah has made your reward binding, and He has returned your land to you. Now do with it whatever you wish."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6463