It is narrated from Nafi' (may Allah be pleased with him) that a man picked up something that had fallen on the road, then he came to Abdullah bin Umar (may Allah be pleased with them both) and said: I have found a lost item, what should I do now? Ibn Umar (may Allah be pleased with them both) said: Announce it. He said: I have done so. Ibn Umar said: Do more. He said: I have done a lot. Then Ibn Umar (may Allah be pleased with them both) said: I do not permit you to eat such a thing; if you wished, you would not have picked it up.
Hadith Referenceمسند الإمام الشافعي / كتاب الرهن والقراض والحجر والتفليس واللقطة / 1488
Hadith Takhrijاسناده صحيح : اخرجه البيهقي: 6 / 188 - وفى المعرفة السنن والآثار له (3824) وابن ابي شيبة (21634)۔ مالك فى الموطا الأقضية، باب القضاء في اللقطة۔