Abu Ubayd (may Allah have mercy on him) said: Regarding the hadith, I have nothing other than what Abd al-Rahman bin Mahdi (may Allah have mercy on him) said: that the one who finds it (the lost property) must announce it forever; otherwise it is not lawful for him to touch it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب اللقطة / 12120