Engaged persons are but people who are marriageable to each other, except that there is a promise of marriage between them. Therefore, they are not allowed to shake hands with each other as they are not yet lawful to one another.

The Prophet, sallallaahu ‘alayhi wa sallam , said: “If one of you were to be stabbed in the head with an iron needle, it would be better for him than touching a woman whom he is not permitted to touch.”

Allaah Knows best.