Salam
There seems to a mental block. Christians believe trinity is clearly described in Gospels, and holy spirit is 1/3 of God or God or a god or a job description of God. As such when Jesus (a) talked about the praised one (which is what Mohammad (s) means) coming after him and him being the holy spirit, the Christians go see it can't be about Mohammad (s), it's about the holy spirit.
Today I am going to challenge this view. Mainly, it's to look at the holy spirit as an occupied position by the chosen and anointed kings from humanity.
John 9:5 FBV
"While I'm here in the world I am the light of the world.”
The context:
As Jesus was passing by, he saw a man born blind. 2His disciples asked him, “Rabbi, why was this man born blind? Was it him who sinned, or was it his parents?”
3Jesus replied, “It wasn't because of the sins of the man or his parents. But so that what God can do may be shown in his life, 4we have to keep on doing the work of the one who sent me as long as it is still daytime. The night is coming when no one can work. 5While I'm here in the world I am the light of the world.”
This shown that night is when light of God is not bright, and when it's bright and everyone is exposed to it, it's called "day".
Jesus (a) then says he is the light of the world. He didn't say just the light of those who he preached to, but the whole world.
Now, if Jesus is the light of the world, then he is the holy spirit as long as he's here:
Guard the truth that was entrusted to you through the Holy Spirit who lives in us.
Jesus being the light of the world is synonymous with the role of the holy spirit lighting the way for the disciples, except the holy spirit is never not on earth while Jesus is only the light when he is on earth.
So the question is who occupies this position before Jesus and after Jesus?
To this, you have to remember the talk of Moses and Elijah:
Luke 9:30 FBV
Two men appeared in brilliant glory. They were Moses and Elijah, and they began to talk with Jesus.
Matthew 17:4 FBV
Peter spoke up, saying to Jesus, “Lord, it's really good to be here. If you want I'll make three shelters—one for you, one for Moses, and one for Elijah.”
Now those who witnessed Elijah knew he came, but how to prove it to those who did not witness him? For this, Jesus (a) uses philosophy that John (a) is like Elijah (a) and this is to prove Elijah (a) has come.
But how does it prove it. Well they killed John (a) the Baptist and didn't recognize him, and so if Jesus (a) ascends to heaven, it makes sense that one alive from the household of guidance be here on earth, and so this proves the wisdom of why Elijah (a) was kept alive by God.
Now if you look at the description of the praised/one often translated as comforter, it becomes obvious, it's about a person who will come in the open and teach the truth and remind them in the same way Jesus (a) reminded of the truth.
And of course, like all chosen humans, he will occupy the position of the holy spirit and is also the holy spirit just as Jesus (a) was the light of the world so long as he was in this world.
Mohammad (a) was the light of the world so long as he was in the world. Today, the light of the world is the Mahdi (a) and we await his return in public, while he is here on earth, hidden like Elijah (a) was hidden between Jesus (a) and Mohammad (a) but was the light of the world, just as John (a) was the light of the world before Jesus (a) but people didn't recognize him and killed him (John (a)).
The holy spirit is synonymous with position of the leader:
O God,
surely Thou hast confirmed Thy religion in all times
with an Imam whom Thou hast set up
as a guidepost to Thy servants
and a lighthouse in Thy lands,
after his cord has been joined to Thy cord!
Thou hast appointed him the means to Thy good pleasure,
made obeying him obligatory,
cautioned against disobeying him,
and commanded
following his commands,
abandoning his prohibitions,
and that no forward-goer go ahead of him
or back-keeper keep back from him!218
So he is the preservation of the shelter-seekers,
the cave of the faithful,
the handhold of the adherents,
and the radiance of the worlds!
-Du'a of the day of Arafa, Sahifa Sajjadiya
And as one of the subtle miracles of Quran
And Zakariya and Yahya and Isa and Elyas, all of the righteous. (Quran, in chapter 6)
Elyas (a) (Elijah) is mentioned two times in Quran, and this is one of the places.
Yahya (John) (a) succeeded Zakariya (a), Isa (a) succeeded Yahya (a), and Elyas (a) although before Jesus (a) was born, takes on the position of the holy spirit AFTER Jesus (a) leaves to heaven.
This verse is a miracle, and to understand it, like many verses in Quran, is to understand the essence of Islam.