What is tarjīʿ, and is it performed when reciting the Qur’an, given that it has been reported that the Prophet, peace and blessings be upon him, used to perform it?

The Ahadith indicate that the intended meaning of the Prophet's (peace and blessings be upon him) tarji' (reverberation) in reciting the Qur'an is to beautify the voice and chant it melodiously, repeating the sound from the throat while fully extending the madd (vowel prolongation), as explained by Abdullah ibn Mughaffal. This was an intentional act and not due to the shaking of the camel. It falls under the beautification of the Qur'an with pleasant voices, attracting hearts to listen and comprehend.