Abdullah bin Adam says: A freed slave of Sayyiduna Anas bin Malik (may Allah be pleased with him) died in the evening, and Sayyiduna Anas (may Allah be pleased with him) said: Place something made of iron on his stomach.
Imam al-Sha'bi (may Allah have mercy on him) narrates that he was once asked about placing a sword on the stomach of the deceased, and he said: It is placed out of fear that he may swell.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6610