Is it true that whoever says "Allahu Akbar" immediately after the Imam receives 5,000 good deeds?

There is no hadith stating that whoever says the takbir immediately after the Imam will receive five thousand good deeds. However, there are narrations about the virtue of catching the opening takbir (Takbirat al-Ihram). Al-Tirmidhi narrated from Anas ibn Malik, may Allah be pleased with him, that the Messenger of Allah, peace and blessings be upon him, said: "Whoever prays to Allah for forty days in congregation, catching the first takbir, will be granted two immunities: immunity from the Fire and immunity from hypocrisy." Al-Albani graded it as hasan (good). It was also narrated from Mujahid that a man from the Companions of the Prophet, peace and blessings be upon him, said to his son: "Did you catch the first takbir?" He replied: "No." He said: "What you missed is better than one hundred black-eyed camels."