Akbar and Birbal puzzle - What is missing in heaven ??

Emperor Akbar once ruled over India. He was a wise and intelligent ruler, and he had in his court the Nine Gems, his nine advisors, who were each known for a particular skill. One of these Gems was Birbal, known for his wit and wisdom. The story/puzzle below is one of the examples of his wit. Do you have it in you to find out the answer?Read on the puzzle and guess the answer....

Emperor Akbar was very fond of Birbal as were many of the village people. However, this made quite a few of Akbar's other ministers jealous.

One day, they decided to come up with a plan to rid them of the "great" Birbal. To avoid suspicion from falling on them, they took the help of the emperor's barber in this plan.

A week later, while Akbar was receiving a haircut, the barber lightly mentioned that he knew of someone who could allow Akbar to reach and even converse with his ancestors who had passed away, but he also stated the man who would go to the heavens would have to be witty, intelligent and wise. Akbar instantly recommended Birbal for the task.

Birbal was told that a fire would be lit around him and the smoke would carry him to heaven; however, chanting would protect him from burning to his death. Birbal instantly knew that this was a plan to get rid of him, but not wishing to anger the emperor, he agreed to perform this task in a month. During this period of time, he asked some laborers to build a tunnel connecting his house to the cemetery, where the "rites" would be held.

When the day came, Birbal escaped his death by going to his house where he stayed for a month growing out his beard. A month later, he went back to Akbar's palace. When asked about the health of Akbar's ancestors, Birbal replied that they were doing very well but were missing just one thing.

What did Birbal say they were missing in heaven?