What is the Sharīʿah ruling on someone who took small cats out of his house onto the roof, despite knowing the possibility of them being harmed or perishing, and then they died, and he believes he bears the burden of sin for that, and feels remorse; is he sinful, and what should he do to expiate his sin?

We ask Allah to remove from you the fear and dread caused by the death of the cats. It would have been better not to deprive them of living in your home until they grew up, for there is a great reward in caring for animals. We hope that no sin will befall you, as long as you did not intentionally harm the animals, but rather did what you did thinking it would not lead to their death. The woman was tormented because she confined the cat and withheld food and drink from it. You should increase in seeking forgiveness (Istighfar), repentance, and good deeds.