To "testify" is to speak in church about a religious experience. The practice is common in black churches and is a very powerful spiritual experience, as members of the congregation share their stories of how God has touched their lives.
This was the first single released on The Isley Brothers' own label, T-neck records.
Jimi Hendrix, known then as Jimmy Hendricks, is featured on guitar. The 21 year-old unknown was touring as a backup musician with The Isleys at the time.
"Won't Get Fooled Again" by The Who is about a revolution, but it doesn't have a happy ending, since in the end the new regime becomes just like the old one. Pete Townshend thought that whoever was in power was destined to become corrupt.