Hanuman Chalisa a Hindi poem primarily praising Lord Hanuman, is Tulsidas's (1532-1623) most famous and read piece of literature apart from the Ramacharitamanasa.
It has gained enormous popularity among the modern-day Hindus. Many of them recite it as a prayer every day (or every week, generally on Tuesdays or Saturdays). Hanuman is a bachelor deity and many bachelors are staunch devotees of Shri Hanuman.
It is believed that the person who chants the Hanuman Chalisa 100 times daily for 100 days will become free from the cycle of birth and death and enjoy the highest bliss, as stated in verse 38.