Hebrews 10:25:
Not forsaking the assembling of ourselves together, as the manner of some is, but exhorting one another: and so much the more, as ye see the day approaching.
See also:
The Importance of a Good Local Church
Balance: Avoiding Ditches on Either Side of the Road
Don’t Believe These Alcoholics Anonymous Lies
If I Get Seriously Ill, Should I Tell Other People?