[Surah Al-Qalam 68:4]
Abdullah ibn Masud narrates in Imam Bukhari, Abu Dawood:
“We were traveling with the Prophet ﷺ and he took a break at a place. He went to attend the call of nature. One Companion noticed a fowl and ran to chase it. The fowl flew away leaving behind two eggs (some narrations say there were two baby birds). The Companion took away both of them and mentioned this to his companions. When the Prophet ﷺ returned, the bird started hovering over his head. Out of hundreds of troops present, the bird chose to hover over the leader only!
He inquired, “Who has snatched away the eggs of the bird and disturbed it?
One of them admitted doing so. Then he instructed, “Return the eggs to the bird. (Show) mercy, mercy!”
The bird knew who was the leader and what kind of authority he had. So, it went to the supreme leader instead of going to the person who had snatched her eggs. The bird was divinely inspired to approach the Prophet ﷺ, The Mercy to all Worlds, who did not tolerate distress of even a bird.
It was asked to him, “Whose Islam is the best?”
He replied, “One from whose hands and words, people are safe.”
He also said, “Whoever does not show mercy to others, no mercy will be shown to him, too.”
A man came and told the Prophet ﷺ, “Whenever I slaughter my goats, I show mercy towards them by sharpening my knife properly.”
He replied, “Allah will show you more mercy because of this kindness.”
We slaughter animals because Allah has permitted us, but our slaughtering should be in the same way as we have been taught by our Prophet ﷺ; to minimise the suffering of the animals.
We have created cattles for you to be useful for you in - Traveling, carrying load, dressing from their skins, eating from their meat and drinking their milk.
Islam does not allow to torture animals while slaughtering them to be eaten. There are educated civilisations even today where people fry live fish, snakes and even fowls.
No wonder Prophet Mohammed ﷺ is honoured with the title, A Mercy to Entire Universe.