Abu Ubayd (may Allah have mercy on him) says: 'Umra means that a man says to another man: This house is yours as long as you live, or he says: This house is yours as long as I live. Something similar is also reported from Ata' (may Allah have mercy on him) in explaining 'umra.
Abu Ubaydah (may Allah have mercy on him) says: Regarding ruqba, Abu al-Zubayr (may Allah have mercy on him) said: Ruqba is that a man says: If you die before me, this will return to me, and if I die before you, it is yours.
Qatadah (may Allah have mercy on him) says: Ruqba is that someone says: This is for so-and-so, and if he dies, it is for so-and-so.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الهبات / 11990
Mujahid (may Allah have mercy on him) says: 'Umra is that a man says to another: It is yours as long as you live. When he says that, it becomes his and his heirs'. And ruqba is that a person says: It belongs to whichever of us two dies last.
The Shaykh says: In his old position, Imam al-Shafi'i (may Allah have mercy on him) followed the apparent meaning of what al-Zuhri narrated, namely that he gives it to him and his heirs. If he did not mention the heirs, he said in one place that it is void, and in another place he said: When the recipient dies, it returns to the giver. Then in his new position he followed the other narrations, which show that when he gives it to him for his lifetime and hands it over to him, it belongs to him and his heirs. This is the (adopted) position, and the same applies to ruqba.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الهبات / 11991