There is a great emphasis on the importance of davening with a Minyan. It's no small thing to be able to say Kaddish and Kedusha and Barechu with ten Jews. Simply put, such prayer brings down the Shechina, the Divine Presence. The Talmud in Gittin proves this point during its discussion of the Canaanite slave and the prohibition of letting him free. The Torah commands us that we are to enslave them under the heading of בהם תעבודו, that they should work for you. Nevertheless, the Gemara brings a case of Rabbi Eliezer who brought his Canaanite slave to Shule only to find nine people for the Minyan. He freed his slave to make the Minyan. The Rabbis ruled that even though it is a Torah commandment of בהם תעבודו, the needs of the community, even though prayer is rabbinical, overrides the Torah's positive commandment.