Elders

[1 Pet. 5:1] The elders which are among you I exhort, who am also an elder, and a witness of the sufferings of HaMashiach, and also a partaker of the glory that shall be revealed:
The idea of the elder came into church life from Jewish culture (Exodus 3:16, 12:21, 19:7). The word "elder" simply speaks of the maturity and wisdom that an older person should have, making them qualified for leadership. One could not even become an elder until they were at least 30 years old with the experiences life has taught. In its application, it is more about wisdom and maturity than age.
It was the practice of Paul and Barnabas to appoint elders in the churches they had founded (Acts 14:23). There was also the development of the office of pastor, who was essentially a teaching elder (1 Timothy 5:17) who appointed and guided elders and other leaders (1 Timothy 3:1-13, 2 Timothy 2:2, Titus 1:5-9).
Those whose office it is to teach others ought carefully to study their own duty, as well as teach the people theirs.
Peter is qualified to speak because he is a fellow elder. Though Peter was clearly the prominent disciple among the twelve, he claims no special privilege or position.
Peter saw both suffering and glory in the life of Y’Shua, he can speak with the authority of an eyewitness. His higher dignity as an apostle is herein delicately implied, as eye witnessing was a necessary qualification for apostleship: compare Peter's own speeches, Acts 1:21, 22; 2:32; 10:39. That is why the Hebrews did not accept Paul as an apostle of the Messiah, so Paul went to the Gentiles.
And elder is to feed the flock promptly and heartily, without selfish motive of gain seeking, as the Israelites gave their services willing-heartedly to the sanctuary. It is important for shepherds - pastors - to realize that they lead Y’Shua' sheep. He is the Shepherd, He is the Overseer, the shepherd doesn't work for the sheep, and he works for the Chief Shepherd.
We are proud of our humility, vain of our meekness; and, putting on the saintliest look; we wonder whether all around are not admiring us for our lowliness. True humility is shown by our ability to cast our care upon G-d. It is proud presumption to take things into our own worry and care about things that G-d has promised to take care of (Matthew 5:31-34).