Protestants and Sola Scriptura adherents: When was scripture alone sufficient? Sola Scriptura is defined as "the Protestant Christian doctrine that the Bible contains all knowledge necessary for salvation and holiness."

Is the concept of Sola Scriptura only applicable to Christians under the New Covenant, or (in hindsight) would it have also applied to Jews under the Old Covenant (e.g., Mary, David, Moses, etc.)?

In other words, scripture (the written word of God) alone was sufficient for Jews in the Old Covenant, or contrarily, it wasn't sufficient for them but it suddenly became sufficient for Christians in the New Covenant. Which would it be?
Protestants and Sola Scriptura adherents: When was scripture alone sufficient?

There is a picture of the Bible being sufficient given in the parable of the rich man and Lazarus.


  Luke 16:31  And he said unto him, If they hear not Moses and the
  prophets, neither will they be persuaded, though one rose from the
  dead.


We see that even the Old Testament was sufficient for one to be inclined to receive Jesus.


  John 5:46  For had ye believed Moses, ye would have believed me: for
  he wrote of me.


The Old Testament was sufficient for people to hear about God and his promise and to trust in that promise.


  Hebrews 11:6  But without faith it is impossible to please him: for he
  that cometh to God must believe that he is, and that he is a rewarder
  of them that diligently seek him.   
  
  Hebrews 11:32  And what shall I more say? for the time would fail me
  to tell of Gedeon, and of Barak, and of Samson, and of Jephthae; of
  David also, and Samuel, and of the prophets: