LadyFatima
As far as i know this topic or hadith has been misunderstood by muslims. i would very briefly tell you what a scholar said about this. first these are not division as you are implying here, it is merely a group of muslims trying to fullfil or attend to some specific needs of the ummah. for example the Tableeq group have done much to get many muslims [and even non muslims] off the streets. Al itihad is concerened with the unity of the muslim ummah, and so are other groups. so this is not divisions among the muslims, it is just a fulfillment of a need within a particular area and time.
The hadith you quoted about 73 divisions is also misunderstood. this hadith does not mean that the above groups, which in the real sense are all doing good service for the deen, are divisions. what one scholar [whose name i cant recall now] actually says is that the division would not necessarily occur in the same period. it means that the divisoin would occur over several period of time from the time of the death of the prophem [scw] untill the end hour.
my advice to you all is that plse be careful about this topic, the enemy of islam want to take advantage of you by showing you division among the muslims.
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salaam all