What does Mark 14:13 mean?
Jesus and the disciples are most likely on the Mount of Olives, where they have spent every night since they arrived at Jerusalem (Luke 21:37–38). The previous night, they had dinner in Bethany where a woman anointed Jesus' head with costly perfume (Mark 14:3–9). Now they await Passover, which will start at sundown. As Galileans, they follow Leviticus 23:5 and have the Seder meal at twilight on the 14th of Nisan.Location is important. Deuteronomy 16:5–6 says, "You may not offer the Passover sacrifice within any of your towns that the LORD your God is giving you, but at the place that the LORD your God will choose, to make his name dwell in it…" At the time the Mosaic law was written, the Israelites hadn't even entered the Promised Land. Jerusalem didn't become the capital of Israel until the time of David (2 Samuel 5:5). The ark of the covenant wasn't placed on the temple Mount until the time of Solomon (1 Kings 8:1–11). Generations later, Josiah (2 Kings 23:23) and Hezekiah (2 Chronicles 30:1) recognized that the Passover should be celebrated inside Jerusalem. Since every Jewish man was expected to be there, and many brought their families, those who owned property in Jerusalem proper were expected to let out space for the travelers' meals.
Luke 22:8 identifies the two disciples as Peter and John. They easily find the place they are to use as men do not usually carry water. The text isn't clear how Jesus knows where they will celebrate the meal. He may have coordinated with the home owner beforehand or He may be following the leading of the Holy Spirit.
The Passover, while important, doesn't require a lot of work. It isn't a Sabbath day, as is the next day, the first day of the Feast of Unleavened Bread. In fact, you don't have to be ceremonially clean to participate (Numbers 9:10). Although the ceremony grew in complexity over the years, the required food is merely lamb or young goat with unleavened bread and bitter herbs (Numbers 9:11). The most important aspect is that it absolutely must be kept if at all possible (Numbers 9:13).