The New John Gill Exposition of the Entire Bible1 Corinthians 1:6
Even as the testimony of Christ was confirmed in you.
"the testimony of Christ" is meant the Gospel of Christ, which bears
a testimony to his deity, his incarnation, his obedience,
sufferings, and death, his resurrection from the dead, ascension to
heaven, session at God's right hand, and intercession for the
saints; to redemption by his blood, justification by his
righteousness, pardon and atonement of sin by his sacrifice, and
complete salvation by his obedience and death. This, as it had been
preached to the Corinthians, was confirmed and established among
them, by the signs and miracles with which it was attended; by the
extraordinary gifts of the Spirit, particularly of prophecy bestowed
on many of them; and by the internal power and energy of the Spirit,
accompanying and applying it to their souls.