Alqamah or Masruq narrates that Sayyiduna Abdullah (may Allah be pleased with him) said: "No specific words or recitation have been fixed for us in the funeral prayer. Say the takbir as many times as the imam says it, and say good words as much as you can."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9569