It is narrated from Sayyiduna Zayd bin Khalid al-Juhani (may Allah be pleased with him) that he (peace and blessings be upon him) said: "Whoever gives shelter to a stray is himself astray, as long as he does not announce it."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب اللقطة / 12078
Sayyiduna Thabit bin al-Dahhak (may Allah be pleased with him) found a camel and brought it to Sayyiduna Umar bin al-Khattab (may Allah be pleased with him). He ordered him to announce it. Then he returned to Sayyiduna Umar (may Allah be pleased with him) and said: It has kept me busy from my work. Sayyiduna Umar (may Allah be pleased with him) said to him: Go and release it where you took it from.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب اللقطة / 12079
Ibn Shihab (may Allah have mercy on him) said: In the time of Sayyiduna Umar bin al-Khattab (may Allah be pleased with him), stray camels were left to breed; no one took hold of them, until, when the time of Sayyiduna Uthman (may Allah be pleased with him) came, he ordered that they be announced, then they were sold, and when their owner came, he was given their price.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب اللقطة / 12080