How does Jesus Christ admonish and encourage the churches of Sardis, Philadelphia, and Laodicea in Apocalypse 3?

Continuing the prophetic survey of the Asian churches, the glorified Christ commands Saint John to write to the angel of the church of Sardis, identifying Himself as the sovereign Lord who holds the seven spirits of God and the seven stars. He delivers an unsparing diagnosis of their condition, declaring that although they enjoy an outward reputation for being spiritually alive, they are in truth spiritually dead. Christ commands the community to awaken to vigilance and strengthen the things that remain that are on the verge of extinction, because He has found their deeds incomplete in the sight of God. He urges them to recall how they first received and heard the apostolic gospel, demanding strict obedience and sincere penance. If they fail to watch, Christ warns that He will arrive unexpectedly like a thief, catching them unaware of the hour of His visitation. Nevertheless, the Lord notes that a few faithful souls in Sardis have preserved their integrity and refused to soil their garments. He promises that these worthy disciples will walk with Him clothed in white robes, assuring every conqueror that his name will never be erased from the book of life, but will be openly confessed by Christ before the Father and His celestial angels.

Turning to the congregation in Philadelphia, Christ presents Himself under the sublime titles of the Holy One and the True One, who holds the key of David with the absolute authority to open doors that no man can shut and close doors that no man can open. He commends their perseverance, acknowledging that despite possessing only modest strength, they have faithfully kept His word and refused to deny His name. Because of their steadfast devotion, Christ has placed before them an opened door that no adversary can obstruct. Furthermore, He promises that those of the deceitful synagogue of Satan who falsely claim Jewish identity will be compelled to come and bow before their feet, recognizing that Christ has set His divine love upon this faithful flock. Because they have preserved the word of His patience, the Lord pledges to shield them from the severe hour of trial that is destined to test the inhabitants of the whole earth. Announcing that He comes quickly, Christ commands them to cling tightly to what they have so that no one may forfeit or seize their heavenly crown. Every victor will be made an enduring pillar in the sanctuary of God, going out no more, bearing the inscribed name of God, the name of the heavenly New Jerusalem descending from above, and Christ's own new name.

The final communication is addressed to the angel of the church of Laodicea from Christ, who identifies Himself as the Amen, the faithful and true witness, and the beginning of the creation of God. Bishop Challoner explains that these designations reveal Christ as Truth itself, the Word and Son of God and the principle, source, and efficient cause of the whole creation. The Lord utters a devastating condemnation of their spiritual complacency, observing that their works are neither cold nor hot. Wishing they were either completely cold or burning hot, Christ declares that because they are lukewarm, He is on the verge of vomiting them out of His mouth. While the Laodiceans boast of material wealth, self-sufficiency, and lack of need, Christ exposes their pitiful reality: they are wretched, miserable, impoverished, blind, and naked. In His mercy, the Savior counsels them to acquire from Him gold refined by fire so that they may become truly rich, white garments to hide the shame of their spiritual nakedness, and eyesalve so that they may see. Emphasizing that He rebukes and chastises those He loves, Christ commands them to be zealous and do penance. He tenderly depicts Himself standing at the door and knocking, promising that if anyone hears His voice and unbars the threshold, He will enter to sup in intimate communion with him. To the conqueror, Christ extends the sublime reward of sharing His royal throne, just as He conquered and sat down beside His Father upon the heavenly throne.