The following detail has been shared by Swami Saradeshananda in the book: Reminiscences of Sri Sarada Devi.
I used to gather flowers, bel leaves, etc. for Mother’s daily worship. One day I forgot to include tulsi leaves and Mother was very upset. She said, “Haven’t you brought tulsi leaves? How sacred the tulsi is! It sanctifies whatever it is placed on.”
Regretting my error bitterly, at once I hurried and brought some tulsi leaves for her worship. Since then I have been particularly fond of the tulsi all my life. Daily, at the end of her puja, Mother would touch her head to the ground in obeisance to the Master.
After that she would drink the sacred water used in worshipping the Master, and also take a tulsi leaf and a bel leaf from the floral offerings and put them in her mouth.
