One of the seven churches mentioned in the Christian book of Revelation. Although there is evidence that ancient cities held this name, the Biblical reference is related not to the mistranslated "Asia," but to the Hebrew word עשיה "Assiah," which in Kabbalah relates to our body. Sardis is one of the seven "churches" (Greek ἐκκλησία ekklēsia, "place of assembly"), energetic gathering places, called chakras in Sanskrit.
Sardis corresponds to the chakra Vishuddha.
"When the Kundalini has risen to the region of the larynx it grants the power of hearing the voices of those beings that live in the supra-sensible worlds. The Church of Sardis is in the chakra of the larynx; this chakra has sixteen petals. When the Kundalini reaches this height, it flourishes upon our fertile lips made verb." - Samael Aun Weor, The Yellow Book
"The fifth church is Sardis and is related to the thyroid chakra; this is the church of the larynx. When the sacred serpent opens the Church of Sardis, we can then hear in the internal worlds, because the esoteric ear is opened; internally, we then speak the language of the Light and can create with the power of the word. The larynx is a uterus where the word is gestated. The creative organ of the angels is the larynx. The necessary requirements in order to open this church are vigilance, repentance, and good deeds." - Samael Aun Weor, The Major Mysteries
"And unto the angel of the church in Sardis write; These things saith he that hath the seven Spirits of God, and the seven stars; I know thy works, that thou hast a name that thou livest, and art dead. Be watchful, and strengthen the things which remain, that are ready to die: for I have not found thy works perfect before God. Remember therefore how thou hast received and heard, and hold fast, and repent. If therefore thou shalt not watch, I will come on thee as a thief, and thou shalt not know what hour I will come upon thee. Thou hast a few names even in Sardis which have not defiled their garments; and they shall walk with me in white: for they are worthy. He that overcometh, the same shall be clothed in white raiment; and I will not blot out his name out of the book of life, but I will confess his name before my Father, and before his angels. He that hath an ear, let him hear what the Spirit saith unto the churches." Revelation 3:1-6