John Calvin Commentary Acts 16:14

"And a certain woman named Lydia, a seller of purple of the city of Thyatira, one that worshipped God, heard us: whose heart the Lord opened to give heed unto the things which were spoken by Paul." — Acts 16:14 (ASV)

A woman named Lydia. If they had been heard by a few women, this would have been to enter, as it were, by a narrow opening; but now when only one hears attentively and with fruit, might it not have seemed that the way was stopped before Christ?

But afterward, a noble Church sprang from that one small graft, which Paul describes with many excellent commendations. Yet it may be that Lydia had some companions of whom no mention is made, because she far excelled them all. And Luke does not assign as the cause for this one woman showing herself receptive to teaching that it was because she was more intelligent than the rest, or because she had some self-preparation; but he says that the Lord opened her heart so that she might listen and pay attention to Paul's speech.

He had recently commended her godliness; and yet he shows that she could not comprehend the doctrine of the gospel, except only through the illumination of the Spirit. Therefore, we see that not faith alone, but all understanding and knowledge of spiritual things, is the unique gift of God, and that ministers do no good by teaching and speaking unless the inward calling of God is added to it.

By the word "heart," the Scripture sometimes means the mind, as when Moses says, God hath not given thee hitherto a heart to understand. Similarly, in this place, Luke does not only signify to us that Lydia was brought by the inspiration of the Spirit, with affection of heart to embrace the gospel, but that her mind was enlightened, so that she might understand it.

From this let us learn that such is the dullness, such is the blindness of men, that in seeing they do not see, and in hearing they do not hear, until such time as God gives them new eyes and new ears. But we must note the statement that Lydia's heart was opened so that she might listen to the external voice of the teacher.

For as preaching alone is nothing else but the dead letter, so we must beware lest a false imagination, or a show of secret illumination, lead us away from the word upon which faith depends, and in which it rests. For many, so that they may amplify the grace of the Spirit, feign for themselves certain inspired individuals, so that they may leave no use for the external word.

But the Scripture, which joins the ministry of men with the secret inspiration of the Spirit, does not allow any such divorce to be made. Unless Lydia's mind had been opened, Paul’s preaching would have been only literal; and yet the Lord does not inspire her with bare revelations only, but He gives her reverence for His word, so that the voice of man, which might otherwise have been uttered in vain, pierces into a mind endowed with heavenly light.

Therefore, let those fanatical individuals be gone, who, under the pretext of the Spirit, refuse external doctrine. For we must note the balance of moderation which Luke sets down here: that we can have or obtain nothing by hearing the word alone, without the grace of the Spirit; and that the Spirit is given to us, not that He may bring contempt for the word, but rather that He may instill into our minds, and write in our hearts, the faith of it.

Now, if the reason is asked why the Lord opened one woman’s heart alone, we must return to that principle: as many believe as are ordained to life. For the fear of God, which preceded the plain and manifest knowledge of Christ in Lydia, was also a fruit of free election. Geographers say that Thyatira is a city of Lydia situated on the bank of the river called Hermus, and that it was formerly called Pelopia; but some there are who attribute it to Phrygia, and some to Mysia.