Musannaf Ibn Abi Shaybah 33782 — Regarding Those Who Allow Gifting

Sa'id narrates from Qatadah, and at one place I found this narration from Sa'id bin al-Musayyib, that they did not see any harm in selling the right of wala' when it belonged to the mukatib. And they disliked it in the case when it was in the form of freedom.