Assalaamu alaykum. I would be glad if you do not give me the reference of other fatwas. You said in respective fatwas that "An engagement is just a kind of promise for marriage, and it is permissible for each party to annul it." However, there is a hadith that says that if anyone annuls the promise, then they have to give the expiation, Should a person who annulled the promise have to give an expiation or repent?

All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.

We do not know what hadeeth you are referring to, and as far as we know, we are not aware of any hadeeth that carries this meaning.

Nonetheless, some scholars, providing evidence from the Quran, stated that the covenant of Allaah is an oath that requires expiation. As-Sarakhsi from the Hanafi School of jurisprudence, said in Al-Mabsoot, “The same thing applies if one says, 'I take the Covenant of Allaah on me to…'; the covenant is an oath, as Allaah says (what means): {And fulfill the covenant of Allaah when you have taken it.} [Quran 16:91]; meaning if you make an oath. The evidence for this is that Allaah says (what means): {…and do not break oaths after their confirmation.} [Quran 16:91]."  

However, as is clear, the above is not regarding a mere promise such as an engagement. It should also be mentioned that if a person does not fulfill the promise of engagement and annulled it without any reason, it is disliked for him to do so, but it is not forbidden. He has not committed a sin of which he would be required to repent.

Allaah knows best.