It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) said: "When the servant stands for prayer, his sins are gathered upon his head, and when he bows (in ruku'), they scatter."
No one narrated this hadith from Ubaydullah bin Umar (may Allah have mercy on him) except Marwan, and Muhammad bin al-Zibriqan (may Allah have mercy on him) is alone in transmitting it.
Hadith Referenceالمعجم الأوسط / باب الميم / 7314
Hadith Gradingمحدثین:إسناده ضعيف جدًّا، فيه مروان بن سالم
Hadith Takhrij«قال الهيثمي: فيه مروان بن سالم وهو ضعيف جدا «مجمع الزوائد ومنبع الفوائد، ج 1، ص 301»»