Bukhari

Hadith Commentary:
If a person says, "I have a covenant with Allah that I will certainly do such-and-such act," and he intends an oath (qasam) with these words, then if he does not perform the act, he will have to offer expiation (kaffarah).

According to Imam Bukhari rahimahullah, "the covenant of Allah" refers to taking an oath (qasam) by Allah.

In the noble verse as well, "the covenant of Allah" refers to taking an oath by Allah.

If there is no intention of an oath, then in the case of not performing the act, there will be no expiation, because Allah ta'ala has taken a covenant from every legally responsible person (mukallaf) that they will not worship Satan, but rather they will worship only Allah ta'ala.

In any case, in such expressions, the person's intention will be considered.

And Allah knows best. (Fath al-Bari: 11/664)