Does speaking for the benefit of one of the worshippers invalidate the prayer? And what is my obligation?

The questioner : Shaykh, a small question, but regarding speaking in prayer. An incident happened to me once. A man was praying beside me, and he fell out of prayer into a state of dizziness or unconsciousness. So I sat him down and I said to him, in one word, while I was praying, "Sit, my brother, and pray while sitting." And I completed my prayer. I was in the middle of a rak'ah, and this happened, meaning, after that, in the second rak'ah. And I completed my prayer, and I did not repeat the rak'ah, meaning, I completed it normally?

The Shaykh : No, this invalidates the prayer.

The questioner : It invalidates the prayer?

The Shaykh : It is known, unless you were, without blame, ignorant.

The questioner : ... .

The Shaykh : I was ignorant?

The questioner: Yes.

The Shaykh : So then, may Allah forgive what has passed.

The questioner : That is what happened.