"Friend" is another relative term such as "abiding" or "fellowship." A person can be a casual friend, a close friend, or an intimate friend depending on his or her love and loyalty. Likewise all believers are God"s friends in one sense, but abiding believers are His friends on a deeper level because they seek to obey Him consistently (cf. Psalm 25:14). [source][source][source]
A good servant (Gr. doulos, lit. slave) also obeys his master. What then is the difference between a servant of God and an intimate friend of God? Jesus proved to His disciples that they were His friends as well as His servants but pointing out that a master shares his plans with his friends but not with his slaves. He had told them what was coming thereby treating them as His friends. Abraham and Moses, the only Old Testament characters whom God called His friends, also received revelations of God"s plans from Him (cf. Genesis 18:17; Exodus 33:11; 2 Chronicles 20:7; Isaiah 41:8; James 2:23). Jesus also referred to Lazarus as "our friend" ( John 11:11). [source][source][source]
Slaves customarily receive orders but no explanations or reasons for their orders. One of the differences between friends and slaves is the degree of intimacy they share with the Master. Jesus raised His disciples from the level of tools to being partners with Him in His work (cf. 2 Corinthians 5:20 to 2 Corinthians 6:1). [source][source][source]
Jesus said that He no longer called His disciples slaves implying that He had done so in the past. One of the common titles God used for the prophets in the Old Testament was "my servants the prophets" (e.g, Jeremiah 7:25; Jeremiah 25:4; Jeremiah 29:19; et al.). In former times God had not revealed His mind fully to His people (cf. 1 Peter 1:10-12). However with the coming of Jesus He revealed His plans as to friends rather than as to servants. This is another indication that Jesus viewed His Incarnation as the culmination of divine revelation. The revelation that Jesus gave through the apostles following His ascension was a continuation of that revelation (cf. Acts 1:1-2). [source][source][source]