Quiet, please

My evening ritual almost similar every night. Started by taking my daughters, Najla and Zea to the toilet, changing their clothes into pyjamas and ended up by telling them the children stories.

Last night, after finishing the storytelling session, I saw that both of my little girls looked terribly sleepy already. Then, I asked them to go to sleep right away.

me : "Okay girls, it's time to go to bed."
Najla & Zea : "Okay."
me : "Well, girls, before you fall asleep, do you want me to...uhm...sing a lullaby or something?"
Najla : (answer in her sleepy tone) "Ma, just keep quiet."
me : #@$%^&*$#