Just picked up from salafi forum
Anas reported: 'Umar once saw a slave-girl that belonged to us (to Anas) wearing a scarf, so Umar hit her and told her: 'Don't assume the manners of free woman.''
Musnaf Ibn Abi Shaybah, Volume 2 page 41 Tradition 6236
Imam Ibn Hajar in 'al-Deraya' Volume 1 page 124 and Al-Albani the Salafi in 'Irwa al-Ghalil' Volume 6 page 203 have graded this hadith as 'Sahih'.
And Shia sources
This report is declared “Sahih” by the Grand Ayatullah al-Sayyid Muhammad Sadiq al-Ruhani in Fiqh al-Sadiq [4:228]
In fact, it is narrated in Qadi Nu`man al-Maghribi’s Da`a’im al-Islam [1:177] and al-Nuri’s Mustadrak al-Wasa’il [3:217] that Ja`far al-Sadiq was asked about the permissibility for a slave girl to cover her head during prayers and he replied:
“No, When my father, `alayh as-salam, saw a slave girl praying and she had a scarf on her, he hit her! And he said: ‘You rascal! Do not resemble the free ones!’”
Rascal? What does that remind you of?