It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) used to pray on a mat.
Hadith Referenceمسند احمد / ومن مسند بني هاشم / 2472
Hadith Gradingحکم دارالسلام:صحيح لغيره، وهذا إسناد ضعيف، لضعف زمعة