What is the ruling on the the imam's saying before the opening takbir, "Turn your hearts towards Allah" and "Pray the prayer of one bidding farewell"?

It is sunnah for the Imam to straighten the rows himself and to instruct the congregants to do so. There is no need for these phrases if the Imam sees that the row is already straight. We do not know of anything in the authentic Sunnah that instructs the Imam to command the worshippers regarding humility and focusing their hearts before prayer. The Imam's continuous practice of this is feared to fall under the category of innovation (bid'ah), though there is no harm in saying it occasionally. The phrase "وجهوا قلوبكم إلى الله" (direct your hearts to Allah) has no basis. As for "صلِّ صلاة مودِّع" (pray the prayer of one bidding farewell), it has been authentically reported from the Prophet, peace and blessings be upon him, as a general admonition, unrelated to what the Imam says before the takbirat al-ihram.