Possible Clues:

• 'I do,' e.g.
• A letter read out in confession
• I, say, go after a positive declaration
• Statement of belief
• Profession of one of several characters, say
• Promise it's a non-consonantal sound
• Hear there's a letter - the testimony?
• They say it's not a consonant - I swear!
• Frank acknowledgment
• Said perhaps I will make a statement