"So it is with the divine religions: With the passage of time, their original precepts are altered ..."

"In the beginning, this tree was full of vitality and laden with blossoms and fruit, but gradually it grew old, spent, and barren, until it entirely withered and decayed. That is why the True Gardener will again plant a tender sapling of the same stock, that it may grow and develop day by day, extend its sheltering shade in this heavenly garden, and yield its prized fruit. So it is with the divine religions: With the passage of time, their original precepts are altered, their underlying truth entirely vanishes, their spirit departs, doctrinal innovations spring up, and they become a body without a soul. That is why they are renewed."

‘Abdu’l-Bahá, Some Answered Questions