What is the ruling on the Imam raising his voice during the Takbirat of movement in congregational prayer?

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It is recommended (Sunnah) for the Imam to raise his voice during the Takbirat so that the follower (Ma'mum) may hear him and follow him, whether the Imam is praying silently or audibly, similar to the ruling regarding the Takbirat al-Ihram (opening takbir). If the Imam does not raise his voice loud enough for all followers to hear, it is recommended for some followers to raise their voices to inform others, as Abu Bakr, may Allah be pleased with him, did when leading the Prophet, peace be upon him, during his illness while the Prophet sat.