"Jesus said unto him, Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind" (Matthew 22:37).
According to Jesus, this is "the great commandment of the law" and this is also the first verse in the New Testament to associate "love" and the "heart." This "love," of course, is not romantic love (the Greek word for that love is never used in the New Testament at all), but the divine type of love (Greek, agape), as in "God so loved the world."
The "heart" (Greek, kardia, from which come such English words as cardiology) is mentioned often in the Bible, but almost never means the actual physical organ. It refers to the emotional and spiritual components of man's nature--"the hidden man of the heart" (I Peter 3:4). We use "heart" for the same purposes in English. Just how this particular date came to celebrate the heart as a symbol of romantic love and to be called Valentine's Day is uncertain. There were various emperors, popes, and religious leaders named Valentine in the early history of Christendom, including two Roman Catholics designated as Saint Valentine. In any case, Christians should remember that true Christian agape love should be manifested in our lives every day of the year. To that end, "see that ye love one another with a pure heart fervently" (I Peter 1:22). True Christian love can only be expressed out of a heart that has been made pure. As Paul wrote young Timothy, "Now the end of the commandment is charity [that is, agape love] out of a pure heart, and of a good conscience, and of faith unfeigned" (I Timothy 1:5).
And remember that, first of all, we must "love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind, and with all thy strength: this is the first commandment" (Mark 12:30). HMM