Islam encourages people to be loving and peaceful. If that is so, then some of us can think that Valentine’s Day is a day when Muslims can spread love and peace among themselves. So why is it prohibited in Islam to celebrate Valentine’s Day?

Narrated Abu Sa’eed al-Khudri (R.A) the Prophet (peace and blessings of Allah be upon him) said: “You will certainly follow the ways of those who came before you, span by span, cubit by cubit, until even if they were to enter a lizard’s hole, you would follow them.” We said, “O Messenger of Allah, (do you mean) the Jews and Christians?” He said, “Who else? !” (Narrated by al-Bukhaari and Muslim)
The Prophet (peace and blessings be upon him)said: ” Whoever resembles a people in their actions and practices is just like them.” (Abu Dawud 4021, Ahmed 2/50)
Celebrating Valentine’s Day is imitating the pagans. And not only is it imitating the Romans, but the people of the book (Christians) too.