Is the narration that mentions a Companion standing immediately after his prayer and pulling 'Umar ibn Al-Khattāb, saying: "O Allāh, You are As-Salām, and from You comes As-Salām" authentic?

It is recommended for the worshiper to remain in his prayer area after the prayer to perform the remembrances (dhikr), due to the angels' supplication for his forgiveness and mercy that results from it, and to allow women the opportunity to leave first. There is no harm in standing up immediately after the prayer and performing the remembrances on the way. As for the hadith of Umar ibn al-Khattab, may Allah be pleased with him, with the man who prayed a supererogatory prayer immediately after the obligatory prayer, it was a disapproval of connecting the supererogatory prayer with the obligatory prayer without a separation.