أن لا يكون الفرع منصوصاً عليه
The new case must not already have its own ruling stated in an applicable text.
Qiyas is used where a case needs to be linked to an established original by an effective cause. If the new case itself is governed by a valid text, its ruling is determined through that text rather than a competing analogy.
Compare:
1. A new case is directly governed by a text: the text controls.
2. A different case has a textual rule, and the new case shares its operative cause: a valid qiyas may be possible.
The condition preserves textual authority and confines analogy to its proper field.