Question:
What is the difference between the sadiqeen and the sidiqeen? why does Allah sometimes use one instead of the other?
Answer:
The sadiqin means the truthful ones and the siddiqin means the all-truthful ones, an intensive form of sadiqin. One is sometimes used instead of the other in the Qur’an depending on context with regard to subject-matter as well as tone and style.
Hajj Gibril Haddad