Praise be to Allah.
This is an issue that was discussed at length by the scholars of tafseer, and this is not the place to discuss all aspects of this matter in detail.
The correct view concerning this matter is that the usage of the word “nikaah” in the religious texts – that is, the way it is used in the Qur’an and Sunnah, and the way the Sahaabah used the word – more often refers to the marriage contract.
However, that does not mean that it is not used to refer to intercourse – or in a more general sense, embracing and the like. There is no stronger proof than the fact that it is used frequently and is well-known to refer to one of the two things.
The word most often refers to the marriage contract in the Qur’an and Sunnah, and the usage of the Sahaabah, and even among the Arabs before Islam. This is clear and there is no need for any circumstantial evidence to understand it.
See the entry on the word nikaah:
Ibn Taymiyah said: Whenever the word nikaah occurs in the Qur’an, it inevitably refers to the marriage contract, although the meaning of intercourse is also included in it.
As for this word referring to intercourse only, that does not occur in the Book of Allah at all.
End quote from al-Fataawa al-Kubra (3/178).
He refuted at length those who claimed that the word nikaah in the Qur’an refers to intercourse only.
Ibn al-Qayyim said: The word nikaah in the Qur’an can only refer to both the marriage contract and intercourse together. As for it meaning intercourse only, that does not occur in the Qur’an even once.
But when there is a word that may have two meanings, then in the context of prohibition it may apply to either of them, in contrast to the context of enjoining it, in which case it applies to both meanings. Therefore you will not be complying with the prohibition unless you refrain from both, and you will not be complying with the command unless you do both.
The words (interpretation of the meaning) “And do not marry those [women] whom your fathers married” [an-Nisaa’ 4:22] imply that it is forbidden for a person to marry a woman with whom his father did the marriage contract but did not consummate the marriage with her, and that it is forbidden for him to marry a woman with whom his father had intercourse but did not do the marriage contract with her.
The words (interpretation of the meaning) “then marry those that please you of [other] women” [an-Nisaa’ 4:3], “And marry the unmarried among you” [an-Noor 24:32] and “So marry them with the permission of their people” [an-Nisaa’ 4:25] do not refer to the marriage contract without intercourse, or intercourse without a marriage contract; rather they refer to both together.
Mukhtasar al-Sawaa‘iq (329).
And Allah knows best.