"..let us hear no more of the fanatics who make the excuse of the Spirit to reject external teaching. For we must preserve the balance which Luke established here, that we obtain nothing from the hearing of the Word alone, without the grace of the Spirit, and that the Spirit is conferred on us not that He may produce contempt of the Word, but rather to instill confidence in it in our minds and write it on our hearts." --John Calvin, more here
Johnny is commenting on Luke's summary of what happened with Lydia in Acts 16
"The Lord opened her heart (work of Holy Spirit) to pay attention to what was said (work of her mind)