Adam Clarke on Acts 16:14

Lydia, a seller of purple - She probably had her name from the province of Lydia, in which the city of Thyatira was situated. The Lydian women have been celebrated for their beautiful purple manufactures.

Which worshipped God - That is, she was a proselyte to the Jewish religion; as were probably all the women that resorted hither.

Whose heart the Lord opened - As she was a sincere worshipper of God, she was prepared to receive the heavenly truths spoken by Paul and his companions; and, as she was faithful to the grace she had received, so God gave her more grace, and gave her now a Divine conviction that what was spoken by Paul was true; and therefore she attended unto the things - she believed them and received them as the doctrines of God; and in this faith she was joined by her whole family, and in it they were all baptized.