Zainab (PBUH) learned from the Holy Qur’an that the objective of creating man is for him to reach the pinnacle of servitude.
“We did not create the jinn and men except to worship us.” [Qur’an 51:56]
She had seen her parents worshiping and saying night prayers. She witnessed her brother Imam Hussein (PBUH) telling Abbas on the eve of Ashura: “Go to them and ask them to give us one more night so that we could spend tonight praying and beseeching God for forgiveness. God knows that I love saying prayers, reading Qur’an, praying and beseeching His forgiveness.”
These words speak of not duty, but love for worship and prayers.
Imam Hussein (PBUH), who is an infallible figure, at the time of bidding farewell to her sister, says: “My dear sister, don’t forget (to pray for me) during your nocturnal prayers.”  This shows that Zainab had achieved the summit of servitude of God and worship.