On page 44 of the Jehovah's Witnesses book Life: How did it get here? we find the quote:
But any event that has just one chance in 1050 is dismissed by mathematicians as never happening.
Similar quotes appear in other Creationist material. However, it was years before I heard a Creationist actually name this mathematician.  I have been a scientist for decades, and I have never heard a scientist (or mathematician) say any such thing.
They reason scientists don't say it is because such events happen every second of every day. Science commonly uses dramatically larger numbers, and uses them in describing the actions of everyday things.
For example, take a pack of cards, and shuffle it. If you do a good job, then there are a lot of possible outcomes. Specifically, there are 52 * 51 * 50 * . . . * 3 * 2 * 1 ways. That number is 52 factorial, which is about 1068 . That's 1018 times larger than 1050 . Yet there the shuffled pack is!
But, if you were about to play a hand in a card game, the chance the cards will favor you is one in two, or one in six, or some such number. The point here is that the probability of getting a desirable outcome can be far removed from the probability of getting one specific outcome.
If you think that the factorial of 52 is big, allow me to point out that thermodynamics involves taking the factorial of numbers like 1030 . And we aren't calculating gee-whiz things, far removed from real life. We're calculating the disorder in a quart of water. Compared to numbers like that, 1050 isn't even a spit in the ocean.
Even an expensive computer could never examine each and every one of 1050 possibilities. However, there are search techniques which can hunt through problems of that size in perhaps 105 tries. Here is a "weasel" program that does exactly that by using cumulative selection, and here are some other "weasel" programs.
Footnote: The mathematician turned out to be Emile Borel. He discussed the idea in an obscure book aimed at non-scientists, so this was his personal rule of thumb, not a Theorem or a Law.