"Papa you will be home soon. I am praying for you smile. Papa God is hearing our prayers. Do not worry," it continued.
Speaking like a responsible child, the junior Bachchan had written, "I will look after mama, Shweta didi and the house. I am naughty sometimes. I love you papa. Your darling son Abhishek."
Sharing the letter on Twitter, Big B wrote, "T 3549 - Abhishek in his glory .. a letter to me when I was away on a long outdoor schedule."
The two have been one of the most famous father-son duo in the industry and their bond is made on sight.
Most recently, Abhishek also shared a warm message for his father when he completed 50 years in Bollywood.
He raved about Amitabh writing, "Several generations of cinema lovers get to say we lived in the times of BACHCHAN!!!"
Senior and junior Bachchan have starred in a number of films together including 'Paa', 'Sarkaar', 'Bunty Aur Babli', 'Jhoom Barabar Jhoom', amongst others.