Complex sentence: They attempted to get the Banu Sulaym to attack the Muslims, but the tribe gave them only 700 men, since some of its leaders were sympathetic towards Islam; the Bani Amir refused to join them all together, as they had a pact with Muhammad.
Split into simpler sentences: They attempted to get the Banu Sulaym attack the Muslims, but the tribe gave them only 700 men, since some of its leaders were sympathetic towards Islam. The Bani Amir refused to join them all together, as they had a pact with Muhammad.