The Prophet (peace and blessings be upon him) said:
"Whoever keeps a stray animal with him without announcing it is himself astray, so long as he does not announce it."
Hadith Referenceصحیح الجامع الصغیر / حرف الميم / 5926
Hadith Gradingالألبانی:صحيح
Hadith Takhrij[حم م] عن زيد بن خالد. مختصر مسلم ١٠٦٢.