It is narrated from Sayyiduna Jabir (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) granted us permission, and he did not mention the rope.
There is doubt about whether this hadith is marfu' (attributed to the Prophet), and there is weakness in its chain.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب اللقطة / 12099