It is appropriate to leave a blessing, prayer or encouraging Bible verse in a baptism card. However, different Christian denominations practice baptism differently. For many denominations, baptism is a form of infant dedication, while for others, it is a decision made by a teenager or adult. The age and form of baptism affect the type of message written in the card.
When selecting and writing in a baptism card, it is important to consider whether it is a message that person is likely to receive and read that day, or if, in the case of an infant, it is more likely to be read by the parents and perhaps by the child when he is much older.
If the card is for an infant's baptism, consider a short note of good wishes such as, "May today be a memorable day for your family and a blessing to [infant's name]." A writer who is especially close to the child or is a godparent may want to write a longer blessing, such as "As you grow physically and spiritually, may the Lord bless you and keep you. You are loved by all of your family. God bless you now and always."
If the baptism card is for an adult or teenager, it is appropriate to congratulate him on his decision to follow Jesus, affirm love for him and add an encouraging Bible verse.