Does Shafi'i hold the view that waqf is not valid except through verbal declaration, and that intention alone is not sufficient? And does this apply to gifts and other financial transactions?

The صيغة (expression or declaration) is one of the pillars of the waqf contract according to the Shafi'is. For its validity, it requires a clear verbal utterance, either explicit or implicit, like the words for freeing a slave or other acts of transferring ownership. Al-Nawawi holds that a waqf is not valid except through verbal declaration because it involves the transfer of ownership of both the asset and its usufruct. As for the Malikis and Hanbalis, they believe that an action can take the place of speech; thus, building a mosque and permitting prayer in it is sufficient for it to be considered a waqf.