If he said to his wife, “You are thrice haraam for me,” what is the ruling on that?

Firstly: 

If a man says to his wife, “You are thrice haraam for me,” this wording is
regarded as a metaphor.

With regard to metaphors, reference is to be made to the husband’s
intentions. If what he intended by these words was zihaar [a jaahili form of
divorce in which the husband says to his wife, “You are to me as my mother’s
back”], then it is zihaar. If what he intended thereby was talaaq (divorce),
then it is talaaq. If what he intended thereby was an oath, then it is an
oath.

 Ibn
Qudaamah (may Allah have mercy on him) said: 

It was narrated from Ahmad – with regard to a man who says to his wife, “You
are haraam for me” – that if he intended divorce, then it is divorce. So it
is as if he made it a metaphor for divorce, so it counts as a divorce if
that was his intention. 

If he did not intend divorce, then it is not a divorce under any
circumstances, because it was not a clear statement of divorce, so if he did
not intend divorce, then it does not count as such, as is the case with all
other metaphors.

End quote from al-Mughni (7/318) 

He (may Allah have mercy on him) also said:

If he says, “You are haraam for me”, if he intended thereby zihaar, then it
is zihaar, according to the view of the majority of scholars. This was also
the view of Abu Haneefah and ash-Shaafa‘i.

End quote from al-Mughni (8/8) 

Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said in ash-Sharh al-Mumti‘
(15/153): 

What he says to his wife, “You are haraam for me” may mean one of four
things: 

1.he intended zihaar

2.he intended talaaq
(divorce)

3.he intended an
oath (yameen)

4.he did not intend
anything.

If he intended zihaar, then it is zihaar; if he intended talaaq, then it is
talaaq; if he intended an oath, then it is an oath. What matters in our view
is the words of the Prophet (blessings and peace of Allah be upon him):
“Actions are but by intentions and each man will have but that which he
intended.” 

If he did not intend anything, then it is an oath. The evidence for that is
the verse in which Allah, may He be exalted, says (interpretation of the
meaning): “O
Prophet! Why do you ban (for yourself) that which Allah has made lawful to
you, seeking to please your wives? And Allah is Oft-Forgiving, Most
Merciful. Allah has already ordained for you (O men), the dissolution of
your oaths” [at-Tahreem
66:1-2]. 

For more information, please see the answer to question no.
81984 

Secondly: 

What appears to be the case with regard to your husband saying to you, “You
are haraam for me” is that what was intended was divorce, based on the fact
that he mentioned the number three (“thrice”). It is as if he intended a
threefold divorce, and circumstantial evidence may clarify what is meant by
metaphors. 

See: Kashshaaf al-Qinaa‘ (5/253). 

 Based on that, is it one divorce or three divorces? 

There is a difference of scholarly opinion concerning that. The view
favoured on this website is that it is one divorce, so the husband may take
back his wife during the ‘iddah, if this was a first or second divorce. 

For more information, please see the answer to question no.
152067

And Allah knows best.