I've often wondered what non-Jewish charities think when checks come in for $18, $36, or $54. These amounts may appear random, but they are anything but. Chabad explains:
Eighteen is the numerical value of the Hebrew word "chai" which means "life." It is a Jewish custom to give monetary gifts in increments of 18, thus symbolically blessing the recipient of the gift with a good long life.
This word to number conversion isn't just restricted to the word life. Any word can be mapped to a series of digits and interpreted. The practice is known as Gematria:
Because every letter of the alphabet has a numerical value, every word also has a numerical value. For example, the word Torah (Tav-Vav-Reish-Hei) has the numerical value 611 (400+6+200+5). There is an entire discipline of Jewish mysticism known as Gematria that is devoted to finding hidden meanings in the numerical values of words.
Any Rabbi worth his salt will have many word to number, and number to word meanings memorized. This comes in handy when someone shares that today is, say, their 34th birthday. "Such good luck!" he can exclaim and then go on to explain that the word for "to be strong, powerful; strength" also adds up to 34. See, it's a sign!
This morning, after morning minyan I wanted to drop a special amount in the in pushke in honor of my Father-in-Law's English yahrzeit (Z"L). I suppose I could have asked one of the Rabbis present for some Gematria suggestions but instead I asked Google. And while Google has many features built in, it doesn't yet calculate Gematria on the fly. But, it did put me to this handy web page: Hebrew Gematria: Values from 1 - 99.
And so I spent a few minutes browsing the list, looking for a word or phrase that would capture my Father-in-Law.
In the end, I dropped a $10 bill in the pushke. My reasoning goes like this. One Gematria for 5 is: "to introduce a question: that." And if there's one principle my Father-in-Law taught me it was the importance of asking questions. Don't just accept the what you're told; question it! And so two 5's--double asking questions--seemed like just the right sentiment.