It is narrated from Sayyiduna Abdullah bin Salam (may Allah be pleased with him) that he said: "Whenever hardship befell the family of the Prophet (peace and blessings be upon him), he (peace and blessings be upon him) would command them to pray. Then he (peace and blessings be upon him) recited this verse: 'And command your family to pray and be steadfast in it.'"
This hadith is narrated from Sayyiduna Abdullah bin Salam (may Allah be pleased with him) only with this chain, and Ma'mar (may Allah have mercy on him) is alone in narrating it.
Hadith Referenceالمعجم الأوسط / باب الألف / 886
Hadith Takhrij«أخرجه الضياء المقدسي فى «الأحاديث المختارة» برقم: 434»