Praise be to Allaah.
Many people use the word “engagement” to refer to the period
following the marriage contract and before consummation of the marriage. If
this is what is referred to in the question, then there is no sin on you for
what happened between you, because simply by doing the marriage contract,
the woman becomes the wife of the man and there is no sin on either of them
for enjoying the other.
But if what you mean by engagement is simply promising to get
married and agreeing to do so without doing the marriage contract, then what
happened between you is haraam. During this period Islam does not permit
anything more than looking so that both the man and woman can be sure that
they want to go ahead and get engaged. What you both have to do – in this
case – is to repent, seek forgiveness and regret these actions. The marriage
contract between you is not sufficient to expiate for these sins, rather you
have to repent and seek forgiveness.
With regard to expiation, there is no specific expiation for
what has happened between you, but it is prescribed for the one who repents
to do a lot of righteous deeds such as offering naafil prayers, fasting,
giving charity and so on. Allaah says (interpretation of the meaning):
“And verily, I am indeed forgiving to him who repents,
believes (in My Oneness, and associates none in worship with Me) and does
righteous good deeds, and then remains constant in doing them (till his
information please see the answers to questions no.
And Allaah knows