About 120 believers were gathered on the Day of Pentecost shortly after the ascension of Jesus Christ.  That particular Day of Pentecost marked the actual beginning of the visible Christian church. The disciples of Christ were assembled, and the Holy Spirit came upon them, making them the new temple of the Triune God.  Looking past the thousands of groups and denominations, there is only one church of Jesus Christ. It comprises all congregations of believers in Christ in which the pure Gospel is preached, the sacraments are duly administered, and the discipline of the Christian fellowship is maintained with purity.
Surely those gathered represented the Christian elite of that time, having the spiritual acumen of James Arminius and John Wesley, the ethical and moral strength of Mother Teresa and the structured theology of Richard Watson and H. Orton Wiley.  Surely these persons were at least the equivalent of modern day, ordained ministers who endure years of theological study and examinations by various councils of authority.
But wait.  Consider the description given by C. W. Carter:
“The 120 disciples awaiting the effusion of the Spirit included such diverse individuals as the impetuous and vacillating Peter; the hot-tempered James and John (sons-of-thunder), who at one time wished to burn up the Samaritans (Luke 9:53-54); the empirically disposed, doubting Thomas; Matthew, a former publican of dubious honesty; Simon Zealotus, a former member of a guerilla outlaw gang (Greek, sikarios), who likely had committed murder; Mary, the mild and affectionate mother of Jesus; undoubtedly the wealthy and cultured Mary, mother of John Mark; likely Mary Magdalene of former ill repute, out of whom Jesus had cast seven devils; possibly the “woman of Samaria” who met Jesus at Jacob’s well; and the brothers of Jesus who belatedly believed on Him – to mention only a partial number of the list of those now gathered in “one accord” awaiting the fulfillment of the promise of the Spirit…
Thus, the recipients of the first Christian Pentecost were the saved disciples of Jesus Christ, regenerated by the Holy Spirit, separated from the world, and designed by Christ to become the living evangels of His lordship to all men, subsequent to their baptism with the Spirit at Pentecost.”
Perhaps the rulers and authorities in Heavenly realms thought to themselves, “This looks like a strategic disaster; most likely Jesus has formulated another plan.  These men and women are ordinary, unremarkable, flawed, inconsistent and untrustworthy.  Surely the outcome of the Great War between good and evil cannot be allowed to depend on this rag-tag bunch of misfits.”  But, in fact, there was nor is no other plan!  It is difficult to avoid the conclusion that those present were entirely sanctified by the Holy Spirit on that day.  (See also Sections 3.6, 3.15, 3.17, 4.5, 4.6, 11.7 and 13.13 of Theology Corner)