Is the claimant of preemption (*shuf'a*) required to provide evidence of his partnership status?

Primary text

The claimant of preemption must establish evidence proving his partnership status when the purchaser denies the existence of partnership in the acquired share. This position is held by Abu Hanifa, Muhammad, and Al-Shafi'i. Evidence is required because ownership (*milk*) is not established merely by possession (*yad*). If the ownership required for preemption is not proven, preemption cannot be established, as mere appearance is insufficient, similar to a claim regarding a slave woman's child being in possession.