'Umra' means that a man says to another man: It belongs to you so long as you live. When he says that, it belongs to him and to his heirs. Ruqba means that a man says to another: From me and from you.
أَنْ يَقُولَ الرَّجُلُ لِلرَّجُلِ هُوَ لَكَ مَا عِشْتَ فَإِذَا قَالَ ذَلِكَ فَهُوَ لَهُ وَلِوَرَثَتِهِ وَالرُّقْبَى هُوَ أَنْ يَقُولَ الإِنْسَانُ هُوَ لِلآخِرِ مِنِّي وَمِنْكَ