A mitzvah is a commandment, more, it is something understood as an action that enriches ourselves, our lives, others. In the strictest sense, it is one of 613 commandments we were given in the Torah, but more, it is about doing good, being good. Eating kosher food and keeping the Sabbath are mitzvot (plural of mitzvah), but performing an act of kindness, making the decent choice, the honorable one, these too are mitzvot.
If you give charity, help a friend, etc. - again, a mitzvah. Somewhere along the way, I learned that there is a custom to give someone who embarks on a trip a small amount of money, a symbolic gesture more important for the act than the amount - a dollar, a few shekels and tell them at the end of their journey, they should give it to charity.
By giving them this money, you are making their entire journey a pathway towards fulfilling a mitzvah and in making the journey a righteous one, there is the belief that God will give extra protection. When our relatives come visit, often their friends give them money and tell them to donate it in Israel and (when we remember), we try to give them money to do the same upon their return.
Shmulik came home last week and showed me what someone had done. They took 100 shekels (about $30) and folded the bill into the shape of a heart so that he wouldn't mistakenly use it. This is his "mitzvah money" and he has been told to carry it with him and when he finishes his service, to donate it. That means that all of the journey he is about to take is part of the path towards fulfilling this mitzvah.
Of course, simply serving in the army and protecting this country is a mitzvah, but I thought what a beautiful thought this was, what a special way to wish him safety on his journey, throughout his journey.
Shmulik carries this in his wallet, and will for quite some time. May his journey be a safe one from this day, and each day, until he finishes and is able to deliver this charity to a worthy cause.