"The Messenger of Allah forbade 'Umra and Ruqba." I said: "What is Ruqba?" He said: "When one man says to another: 'This belongs to you for the rest of your life.' But if you do that, it is permissible." (Using translation from Nasāʾī 3728)
نَهَى رَسُولُ اللهِ ﷺ عَنِ الْعُمْرَى وَالرُّقْبَى قُلْتُ وَمَا الرُّقْبَى؟ قَالَ يَقُولُ الرَّجُلُ لِلرَّجُلِ «هِيَ لَكَ حَيَاتَكَ فَإِنْ فَعَلْتُمْ فَهُوَ جَائِزٌ»