This quote, taken out of context, can mislead people into believing that participating in a church's communion service is what provides eternal life.
"Whoever eats My flesh and drinks My blood has eternal life, and I will raise him up at the last day." (John 6:54, NKJV)
Reading just the immediate context gives good reason to believe that Jesus is not speaking literally about flesh and blood.
“Does this offend you? [What] then if you should see the Son of Man ascend where He was before? It is the Spirit who gives life; the flesh profits nothing. The words that I speak to you are spirit, and they are life...." (John 6:61c-63, NKJV)