John 15:13

Love for a friend reaches its zenith when one willingly sacrifices his or her life for that friend. Jesus had spoken of His love for His disciples (John 15:12). He would shortly show them how great it was by making the supreme sacrifice for them. After that, they would not only have His command but also His example to follow.

Really Jesus did more than lay down His life for His friends. He died for His enemies (cf. Matthew 5:43-47; Romans 5:8-10). However in the context of this audience His statement was true as it stands. The most a person can do for a friend is to die for him or her.