The Prophet ﷺ said, "If you were forgiven for what you do to animals, much would be forgiven you."
عن النبي ﷺ قال: لو غفر لكم ما تأتون إلى البهائم لغفر لكم كثيرا.
Ahmad (27486) and Bayhaqi in Shuab (5188) both narrated it from the hadith of Haytham bin Kharija, who said, "Abu Rabi Sulayman bin Utba Sulami informed us, from Yunus bin Maysara bin Halabas, from Abu Idris, from Abu Darda," and he mentioned it as a marfu narration. Its isnad is hasan because of Abu Rabi Sulayman bin Utba, for he is hasan al-hadith.As for what Abdullah bin Ahmad said following (27490), after reporting from his father, from Haytham, several hadiths, "Haytham bin Kharija narrated to me, from Abu Rabi, all these hadiths, except that he narrated as mawquf among them the hadith 'Even if what you do to animals were forgiven you' whereas my father narrated it to us from him as marfu," end of quote.So Haytham bin Kharija narrated it in two ways, marfu and mawquf, and the ruling goes to the one who narrated it as marfu.