"9" is symbolic as the largest single-digit number, which is why the Abjad symbolism is related to "BAHA" = "9". God is the greatest, therefore the Abjad of his name is the greatest number.
This would be the qoute:
"First, regarding the significance of the number nine: Its importance as a symbol used so often in various connections by the believers lies in three facts: first, it symbolizes the nine great world religions of which we have any definite historical knowledge, including the Babi and Baha’i Revelations; second, it represents the number of perfection, being the highest single number; third, it is the numerical value of the word ‘Bahá’." (Letter written on behalf of Shoghi Effendi)