Swearing an oath in words that do not represent an oath, but are intended as such
Question

I said to my daughter, “By Allah, you’re gonna get it,” meaning I am going to beat you severely. My husband said to me: “Beat her lightly.” I said: “It is my oath and you are not responsible for its expiation. I said: ‘You’re gonna get it,’ meaning that I am going to beat you severely.” He said: “The meaning of the words should be clear; you said to her, ‘You’re gonna get it’ and you did not say, ‘I am going to beat you.’” I said to him: “This is the way we usually speak.” My husband meant to say that the wording should be clear in order for it to be obligatory to fulfil the oath, and it should not be vague words. If I swore an oath using vague words, saying one thing and meaning another, when in our culture the intention is known, is it obligatory to fulfil the oath, or is it as my husband says?
Praise be to Allah.The oath for which expiation must be offered [if it is broken] is an oath to do something in the future, such as if you say: “By Allah, I will surely beat you” or “by Allah, you’re gonna get it.”
Ibn Qudamah (may Allah have mercy on him) said in al-Muqni‘, p. 461:
In order for expiation to be obligatory, three conditions must be met:
Firstly: the oath should be valid, which means that it should be possible to carry it out or break it. This refers to an oath having to do something in the future that is possible. As for an oath having to do with the past, it is not valid. Such oaths are of two types: [the first of which is] yamin al-ghamus [an oath which will cause a person to be dipped in the hellfire], which is an oath that is sworn, knowing it to be false, for which expiation must be offered; and similar to that is an oath to do something impossible, such as killing one who is dead or bringing him back to life, or drinking water from a jug in which there is no water. [The second type] is an oath by way of idle talk, which means swearing an oath regarding something which the speaker thought to be the case and it turned out to be otherwise. No expiation is required in that case.
Secondly: the oath should be sworn by choice. If a person swears an oath under compulsion, his oath is not valid, and if he says the oath by way of habit, without intending to say it, such as saying “Yes by Allah” and “No by Allah” in the course of conversation, no expiation is required of him.
Thirdly: he should have broken his oath by doing what he swore not to do or not doing what he swore to do, by choice and remembering his oath. If he does that under compulsion or because he forgot, no expiation is required in that case. End quote.
As for your saying, “By Allah, you’re gonna get it,” if you meant to swear that you would beat her, then this is an oath, and if you broke your oath, you have to offer expiation.
Al-Mirdawi said in al-Insaf (11/12): Shaykh Taqiy ad-Din (may Allah have mercy on him) said: The rulings are connected to what people intended when they swore oaths in grammatically incorrect language or very colloquial language [as opposed to formal standard Arabic], and the like.
It says in Kashshaf al-Qina‘ (6/233): If someone says “Wallahu” [instead of the grammatically correct “Wallahi (By Allah)”], it counts as an oath, because according to custom it is an oath and there is nothing to indicate that it is not, unless the speaker is a specialist in Arabic language and did not intend it as an oath, because it is not an oath according to the specialists in Arabic language and he did not intend it as such. But if he did intend it as such, then it is an oath. End quote.
Custom and intention are to be taken into consideration when it comes to oaths.
Talking about beating in this manner is something that is very common among people in many countries, and it is well known in their speech.
Based on that, if it is well known according to custom in your country that saying “You’re gonna get it” refers to a severe beating, then that custom should be taken into consideration, and what you said is subject to expiation.
And Allah knows best.