Shavuos

The Posuk says that the Jews traveled from רפידים & came to מדבר סיני.
Rashi says the reason it tells us they were coming from רפידים, even though we know that, is to tell us that just like when they came to הר סיני, they came in a state of repentance. As it says, they came כאיש אחד בלב אחד; they were all single minded in their readiness to accept the Torah. So too when they left רפידים. 
The Netziv asks, why does it have to tell us what state they were in when they left?
In the Haggada we say that had 'ה brought us to הר סיני but not given us the Torah, דיינו; it would have been enough. How could that be enough? What good would it have done us just to be brought to הר סיני?
Says ר ירוחם ממיר, we are trained to think that the main point of something is the outcome, and the preparation is just the means to get to the end. The Torah here is teaching us that the opposite is true. The main thing in a דבר שבקדושה  is the work you put in. So had we only been brought to הר סיני & been prepared to accept the Torah, that would have been enough.
The gemara tells a story about ר חייא who when there was a fear that the Torah was going to be forgotten, he went and planted flax seed, grew the flax, turned the flax into nets, trapped animals, fed their meat to orphans, & used the skins for parchment to write the Torah on to teach it to the children. 
The gemara asks, why did he go through all that effort when he could have just bought parchment? He wanted to make sure that the Torah would be remembered,  and by putting in all that effort he would be ensured that what was learned from them would be retained & passed on.
Similarly says the Netziv, by any דבר שבקדושה the more one prepares & puts in effort, the more  קדושה will come to him. So by telling us that they were already on the level of כאיש אחד בלב אחד when they left רפידים, it's teaching us that what's important & what matters is the preparation & the work  that we put in, not just the end result!