Sayyiduna Abu al-Darda' (may Allah be pleased with him) narrates this saying of the Prophet (peace and blessings be upon him): "If you were forgiven for the way you treat animals, you would be forgiven for much (of your other shortcomings as well)."
Ahmad recorded it as a marfu' narration (traced to the Prophet), as you see it, while his son Abdullah recorded it as a mawquf narration (stopping at the Companion), and its chain is jayyid (good).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب التوبة / 17468
Hadith Gradingمحدثین:إسنادہ جید
Hadith Takhrij«اخرجه احمد فى المسند (441/6) ، أخرجه مسند أحمد برقم: 26940»