Greetings and blessings,
In response to the notification of your son's, _______, upcoming third birthday, I am attaching an except from a letter from my revered father-in-law and teacher, the Rebbe, with regard to the Jewish customs [appropriate] at that time. May it be G-d's will that you and your wife raise him [and enable him to] attain Torah, marriage, and good deeds amidst prosperity.
With blessing
the Rebbe's signature
This is the quote from my revered father-in-law and teacher, the Rebbe.
With regard to [a child's first] haircut, the upsherinish: It is a matter of great [significance] among the customs of the Jewish people. It's essential purpose is to train [the child to] leave peyos. From the day of the haircut [when] the peyos are left, it is customary to carefully train the child to wear a tallis kattan and to recite the morning blessings, the Grace after Meals, and the Shema before retiring. May G-d assist you to raise your child [and enable him] to attain Torah, marriage, and good deeds amidst abundant sustenance and peace of mind in both material and spiritual matters.