«فَمِنْ مَا مَلَكَتْ أَيْمَانُكُمْ مِنْ فَتَيَاتِكُمُ الْمُؤْمِنَاتِ»
“Then [marry] from among the believing slave women whom you possess.”
The description al-mu’minat (“believing”) qualifies the women addressed. The Shafii analysis makes the attribute relevant to restricting the permissibility of the specified marriage. The Hanafi analysis considers other general or unqualified scriptural evidence and does not derive a universal contrary ruling merely from mentioning the qualification here.
The methodological point is the status of the contrary implication of a descriptive attribute. The explicit case is covered by the words; an unmentioned case requires its own assessment of the available evidence.