Response: This man who kissed this young woman, who is eligible to marry him, without doubt has not practised the wisdom behind fasting. This is because this man has committed an evil act and the Messenger (sal-Allaahu 'alayhe wa-sallaam) said ((One who does not abandon evil talk and actions and ignorance then Allaah is not in need of him abandoning food and water (whilst fasting) )). So, if he does this, then it is disliked and he has committed an evil and ignorant act. In fact, his fast has lost
the wisdom (behind it) and is short on reward, without a doubt. However, according to the majority of the people of knowledge, this does not nullify the fast, which means we cannot order him to make up the fast. As for the one who asked the question, then he must advise the man who committed this act to repent to Allaah (subhaanahu wa-ta'aala). This action is impermissible (muharram) and leads the heart to align with creation and forget the repentance of Allaah (subhaanahu wa-ta'aala) and with that he opens himself to great Fitnah.
Shaykh Ibn 'Uthaymeen
Fataawa Ramadhaan – Volume 2, Page 515, Fatwa No.479;
Fataawa ash-Shaykh al-'Uthaymeen – Volume 1, Page 115-116