[Ruling on Sale by Mutual Transfer (muʿāṭāh) in Non-Trifling Items]

Answer—and Allah is the One who grants success: What appears to me is that such a sale is valid. The proof is Allah Most High’s saying, “except that it be trade by mutual consent among you” [Al-Nisāʾ:29]. Just as they say that consent is an inward matter that must be indicated by wording, here an indicator of the seller’s consent and the buyer’s consent has occurred; and the verse stipulates nothing beyond consent.
Supporting its validity as well is that Muslims have in practice operated this way; and whatever the Muslims deem good is, with Allah, good.
Moreover, what we have said is the view of Imām al-Muʾayyad Billāh and Imām al-Manṣūr Billāh (peace be upon them), as in Sharḥ al-Azhar. And I have seen from Imām al-Mahdī Muḥammad b. al-Qāsim al-Ḥūthī (peace be upon him) that the familiar contract formulas are not a condition for the validity of a sale; rather, anything that indicates consent—such as “Take it,” “Carry it off,” and the like that indicate consent—suffices.
This may also be supported by the well-known maxim: “It is obligatory to construe Muslims’ dealings and contracts as valid wherever possible.”
Source: Min Thimār al-ʿIlm wa al-Ḥikmah vol.2