It is narrated from Sayyiduna Abdullah bin al-Zubayr (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "Any man who is given something as an umra (a lifelong grant), it belongs to him and to his offspring after him; whoever of his descendants inherits from him will inherit it. And whoever gives something as a ruqba (a grant conditional on survival), it too has the ruling of the umra."
Hafs bin Maysarah (may Allah have mercy on him) narrated it in this way from Sayyiduna Ibn al-Zubayr (may Allah be pleased with them both).
Hadith Referenceالمعجم الأوسط / باب الألف / 474
Hadith Gradingمحدثین:رجاله رجال الصحيح
Hadith Takhrij«قال الهيثمي: ورجاله رجال الصحيح «مجمع الزوائد ومنبع الفوائد، ج 4، ص 157»» «أخرجه النسائي فى «المجتبى» برقم: 3746 / 4، والنسائي فى «السنن الكبرى» برقم: 6539»