The testimony is this, that God gave to us eternal life, and this life is in his Son.
The believer carries inward proof: he has seen his sin and need, beheld Christ's excellency and suitableness to it, felt the power of His word remaking him, and discovered love kindled to God through this revelation. That is testimony no argument can shake.
AI summary
Commenting on 1 John 5:10-13
And this is the record, that God hath given to us eternal life, and this life is in his Son. (12) Now at length he shows what this testimony is that is confirmed with so many witnesses: that is, that life or everlasting happiness is the gift of God, which is the Son, and proceeds from him to us, who by faith are joined with...
Verse 11. And this is the record. This is the sum, or the amount of the testimony (μαρτυρια) which God has given respecting him. That God hath given to us eternal life. Has provided, through the Saviour, the means of obtaining eternal life. ; , . And this life is in his Son. Is treasured up in him, or is to be obtained through him. ; ; ; .