I'm quoting some excerpts from a pdf document titled "Celebrating Valentine's Day" - you can read the full text here.
The Pope designated the day of the death of Saint Valentine, February 14, 270 CE, as a festival of love. Who is the Pope? He is the “the archbishop, the supreme pontiff of the universal church, the successor of Saint Peter.” Look at this “archbishop” and how he prescribed for them the observance of this festival which was an innovation in their religion.
This reminds us of what Allaah says (interpretation of the meaning): “They (Jews and Christians) took their rabbis and their monks to be their lords besides Allaah (by obeying them in things which they made lawful or unlawful according to their own desires without being ordered by Allaah)…”[al-Tawbah 9:31]
It was narrated that ‘Adiy ibn Haatim said: “I came to the Prophet (peace and blessings of Allaah be upon him) wearing a gold cross around my neck. He said, ‘O ‘Adiy, cast aside this idol.’ And I heard him reciting from Soorat Baraa’ah [al-Tawbah] (interpretation of the meaning): ‘They (Jews and Christians) took their rabbis and their monks to be their lords besides Allaah.’ He said: ‘They do not worship them, but when they permit them something they accept it as permitted, and when they forbid them something they accept it as forbidden.’” (Narrated by al-Tirmidhi and it is a hasan hadeeth).
Among the most important symbols of this holiday:
1 – Expressing joy and happiness on this occasion, as on their other major festivals.
2 – Exchanging red roses, which are an expression of love, the “spiritual love” of the pagans or the “love” of the Christians. Hence it is known to them as the Feast of Lovers.
3 – The sending of greetings cards. On some of these cards are pictures of “Cupid”, who appears as a child with two wings, carrying a bow and arrows. This was the god of love of the pagan Romans – exalted be Allaah far above their fabrications and their association of others with Him.
4 – Exchange of words of love and desire in the greetings cards which they send to one another, in verse, prose and short phrases. Some of the cards contain comical pictures and funny words, and they often contain the phrase “be my Valentine”. This represents the Christian concept of this festival after it was taken from the pagan concept.
5 – In many western countries, parties are held during the day and in the evening, where there is mixing of men and women, and dancing. Many of them send gifts such as roses and boxes of chocolates to their wives, friends and those whom they love.
Anyone who looks at what is said above about the myths surrounding this pagan festival will clearly understand the following:
That its origins lie in the pagan beliefs of the Romans, where it was an expression of the spiritual love of the idols which they used to worship instead of Allaah. Whoever celebrates it is celebrating an occasion of shirk on which the idols are venerated. Allaah says (interpretation of the meaning):
“Verily, whosoever sets up partners (in worship) with Allaah, then Allaah has forbidden Paradise to him, and the Fire will be his abode. And for the Zaalimoon (polytheists and wrongdoers) there are no helpers”[al-Maa’idah 5:72]
Someone may ask: why do we Muslims not celebrate this festival?
This question may be answered in several ways:
In Islam, the festivals are clearly defined and well established, and no additions or subtractions may be accepted. They are an essential part of our worship and there is no room for ijtihaad or personal opinion. They have been prescribed for us by Allaah and His Messenger (peace and blessings of Allaah be upon him). Ibn Taymiyah (may Allaah have mercy on him) said:
“Festivals are part of the laws, clear way and religious ceremonies of which Allaah says (interpretation of the meaning): ‘To each among you, We have prescribed a law and a clear way[al-Maa’idah 5:48]
‘For every nation We have ordained religious ceremonies which they must follow’[al-
like the qiblah (direction faced in prayer), prayer and fasting. So there is no difference between joining them in their festival and joining them in their other rituals. Agreeing with the whole festival is agreeing with kufr. Agreeing with some of their minor issues is the same as agreeing with them in some of the branches of kufr. Festivals are the most distinctive things by which religions are told apart, so whoever celebrates their festivals is agreeing with the most distinctive rituals of kufr. Undoubtedly going along with them in their festivals may in some cases lead to kufr. Dabbling in these things, at the very least, is a sin. The Prophet (peace and blessings of Allaah be upon him) referred to the fact that every nation has its own festivals when he said: ‘Every nation has its own Eid and this is our Eid’ (al-Bukhaari , 952, Muslim, 1892).” (al-Iqtidaa’, 1/471-472)
There is no religion which encourages its followers to love and care for one another more than Islam does. This applies at all times and in all circumstances, not just on one particular day. Indeed, Islam encourages us to express our emotions and love at all times, as the Prophet (peace and blessings of Allaah be upon him) said: “If a man loves his brother, let him tell him that he loves him.” (narrated by Abu Dawood, 5124; al-Tirmidhi, 2329; it is saheeh).
And he said: “By the One in Whose hand is my soul, you will not enter Paradise until you truly believe, and you will not truly believe until you love one another. Shall I not tell you of something that, if you do it, you will love one another? Spread (the greeting of) salaam amongst yourselves.” (Narrated by Muslim, 54)
The Fatwa of Shaykh Muhammad ibn Saalih al-‘Uthaymeen (may Allaah have mercy on him)
In recent times the celebration of Valentine’s Day has become widespread, especially among female students. This is one of the Christian holidays. They wear all red clothes, including their shoes, and they exchange red flowers… We hope that you can tell us the ruling on celebrating such holidays. What do you advise the Muslims to do with regard to such things? May Allaah keep you and take care of you.
Celebrating Valentine’s Day is not permitted for several reasons:
1 – It is an innovated celebration which has no basis in sharee’ah.
2 – It calls for people to keep their hearts and minds busy with these foolish things that go against the guidance of the pious predecessors (may Allaah be pleased with them), so it is not permitted on this day to do any of the customs associated with that holiday, whether that be connected to food, drink, clothing, exchanging gifts or anything else. The Muslim should be proud of his religion and not be so weak of character that he follows everyone who makes a noise. I ask Allaah to protect the Muslims from all temptations, visible and invisible, and to take care of us and give us strength. And Allaah knows best.
It's entirely our own choice now when we think it is a miniscule thing to just WISH a person - or just DO something nice for somebody...and who said it has to be a girl/guy thing! It can be a bro/sis thing etc etc.
In the light of all the evidence we have, it is a very clear way forward for Muslims of today... even if they're bedazzled by the "Jazba" magical offers in the country!