Q. What is the ruling for putting an animal to sleep (death) because of old age, weakness, difficulties in walking, etc.
A. Every creation of Allah passes through a phase of old age, weakness, etc. This includes humans, animals, birds and insects, etc. Since this is a natural course of life itself, no one is allowed to end the life of another for this reason. As far as animals are concerned, Islam has enjoined on the Muslims to treat them with kindness and not to harm them.
Abdullah Bin Umar (RA) narrates that the Messenger (SAS) said, ‘There is no man who kills (even) a sparrow or anything smaller, without its deserving it, except that Allah will question him about it’. (Nasai)
In another tradition, Abu Umama narrated that the Prophet (SAW) said, ‘He who takes pity even on a sparrow and spares its life, Allah will be merciful on him on the Day of Judgment (Tabarani).
Based on these and many other Traditions which speaks about kindness to animals, it will not be allowed to kill animals on account of their old age or weakness.
And Allah knows best.
Mufti Waseem Khan
This answer was collected from DarulUloomTT.net, which is operated under the supervision of Mufti Waseem Khan from Darul Uloom Trinidad and Tobago.