The internal witness is one alone

The internall witnesse is one alone: namely, of the holy Ghost inwardly speaking to our heart, and perswading vs that those writings are inspired of God, and sealing them vp in our hearts. Eph. 1.13. and 1. Ioh. 2.20.27. Ye haue an oyntment of the Lord, and this oyntment teacheth you of all things: for whosoeuer are led by the spirit of God, can easily discerne his power speaking in the Scriptures: as it is said 1. Cor. 2.15. The spirituall man discerneth all things: and Esa. 53.1. The arme of the Lord is not reuealed to all men. So Luk. 8.10. and Mat. 13.11. The mysteries of the kingdome of heauen are not reuealed to all men, but to those to whom it is giuen of God. And this testimonie properly maketh for our confirmation, and this alone doth satisfie vs, being knowne of them alone that are conuerted vnto Christ, which doth euermore agree with the Scripture, without which the testimonie of the Church can be of no waight with vs. For as none but God alone is a fit witnesse to testifie of himselfe in his word: euen so the word neuer findeth credite in our hearts, till such time as it be sealed vp vnto vs by the inward testimonie of the spirit.

More modern spelling:

The internal witness is one alone; namely of the Holy Ghost inwardly speaking to our heart, and persuading us that those writings are inspired of God, and sealing them up in our hearts, Eph. 1:13; 1 John 2:20, 27, Ye have an anointment of the Lord, and this anointment teaching you all things. For whosoever are led by the Spirit of God, can easily discern his power speaking in the Scriptures. As it is said, 1 Cor. 2:15, The spiritual man discerneth all things, and Isa. 53:1, The arm of the Lord is not revealed to all men. So Luke 8.10. and Matt. 13.11. The mysteries of the kingdom of heaven are not revealed to all men, but to those to whom it is given of God. And this testimony properly maketh for our confirmation, and this alone doth satisfy us, being known of them alone that are converted unto Christ, which doth evermore agree with the Scripture, without which the testimony of the church can be of no weight with us. For as none but God alone is a fit witness to testify of himself in his word: even so the word never findeth credit in our hearts, till such time as it be sealed up unto us by the inward testimony of the Spirit.

Guillaume (William) Bucanus, Body of Divinity or Institutions of the Christian Religion; framed out of the Word of God, and the writings of the best divines, methodically handled by was of questions and answers, fit for all such as desire to know and practice the will of God. Written in Latin. Translated into English by Robert Hill and Fellow at St. Johns College in Cambridge, for the benefit of the English Nation. Printed at London: By George Snowdon, and Leonell Snowdon [, and R. Field], 1606, pp. 40-41.