Numbers, 9:9-13. God is talking to Moses.
Then the LORD said to Moses, "Tell the Israelites: 'When any of you or your descendants are unclean because of a dead body or are away on a long journey, they may still celebrate the LORD's Passover. They are to celebrate it on the fourteenth day of the second month at twilight. They are to eat the lamb, together with unleavened bread and bitter herbs. They must not leave any of it till morning or break any of its bones, and they must follow all the regulations. But if a man who is ceremonially clean and not on a long journey fails to celebrate the Passover, that person must be cut off from his people because he did not present the LORD's offering at the appointed time. That man will bear the consequences of his sin. (adap. NIV)
That is, Moses is to tell the Israelites that if someone is ritually impure or is away on a long journey and can't make his paschal offering (at the appointed place, which in rabbinic Judaism is the temple in Jerusalem) in the first month of the year (Nissan), he can make it up in the second month (Iyyar).
In the Torah, there is a little dot above the word "long." My new friend Rabbi Yosi explains: it's to teach that "long" doesn't really mean "long."
How so? The ninth chapter of Pesahim; the mishnah asks "So what's a long journey?" R' Akiva says you're a long way from Jerusalem if you're more than a day's walk out. R' Eliezer says you're a long way from the temple if you're not actually in its precincts.
The thing is that if you miss your paschal sacrifice in Nissan because you had a party to go to in Katamon, and then fail to make it up in Iyyar because you had a party to go to in Nahlaot, you're absolutely done for - eternal damnation is yours. But if you missed in Nissan because you were at a business meeting in New York, and missed in Iyyar because of the party in Nahlaot, you're just about okay - you aren't necessarily going to be God's favourite person, but you aren't doomed forever.
Rabbi Eliezer, by defining a long journey as one outside the temple precincts, is being hugely lenient; if someone doesn't make it to the temple in Nissan for the sacrifice because they couldn't find a parking space, and then doesn't make it to the temple in Iyyar because he's babysitting (or going to that party in Nahlaot), is he doomed for all eternity? According to Rabbi Akiva, yes he is, but according to Rabbi Eliezer, no he isn't. Rabbi Eliezer's teaching serves to make eternal damnation just that little bit less likely for all of us.
This is what Rabbi Yosi is saying; the little dot over the word long is there by way of commentary - sometimes even the shortest distance can be a long journey.