1a] Is it prescribed for the khateeb to say “Aqoolu qawli haadha wa astaghfir-Allaah (I say these words of mine and I ask Allah for forgiveness)?

1a]
''Friday Prayers'' :
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because what these words refer to is everything that the khateeb said
in his khutbah, even the verses, hadeeths and reports thatthe khateeb
quoted.
The point is that saying these words is permissibleand there is
nothing wrong with it, and there is no justification for objecting to
it.
We ask Allah to help us tounderstand His religion properly.
And Allah knows best.