It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them) that he said: When any of you yawns, he should place his hand over his mouth, for it is from Satan.
Hadith Referenceالادب المفرد / كتاب العطاس والتثاؤب / 950
Hadith Gradingالألبانی:صحيح الإسناد موقوفًا
Hadith Takhrij«صحيح الإسناد موقوفًا : تفرد به المصنف»