Scripture

Acts 18:28 For he mightily convinced the Jews, and that publickly, shewing by the scriptures that Jesus was Christ.

What scripture was he using?

G1124 - From G1125; a document, that is, holy Writ (or its contents or a statement in it): - scripture.  Used 51 times in 51 verses, singular and plural.

• G1125 - A primary verb; to “grave”, especially to write; figuratively to describe: - describe, write (-ing, -ten).

Scriptures - plural - used 21 times in 21 verses, all in the New Testament.

All of which use G1124, except:

2Ti 3:15  And that from a child thou hast known the holy scriptures (G1121), which are able to make thee wise unto salvation through faith which is in Christ Jesus.

G1121 - From G1125; a writing, that is, a letter, note, epistle, book, etc.; plural learning: - bill, learning, letter, scripture, writing, written.

Christ Jesus uses the scripture (Old Testament) to validate Himself.

Joh 5:39  Search the scriptures; for in them ye think ye have eternal life: and they are they which testify of me. 

Barnes Commentary on Acts 18:28:

Showing by the scriptures - Proving from the Old Testament. Showing that Jesus of Nazareth corresponded with the account of the Messiah given by the prophets.

Barnes on John 5:39:

The scriptures - The writings or books of the Old Testament, for those were all the books of revelation that they then possessed.

On the phrase 'search the scriptures':

Search the scriptures - The word translated “search” here means to “search diligently” or “search anxiously.” It was applied to miners, who search for precious metals - who look anxiously for the “bed” of the ore with an intensity or anxiety proportionate to “their sense” of the value of the metal.

How 'anxiously' do I search the Word of God, Old, New or both?  How hungry am I to be 'fed' by His Word.  To immerse myself in His Word?  To be conformed to His image?

Oh Lord, help me to love you, to desire you in all areas of my life, to feast on Your Word daily, to meditate on it.  O' Father cause me to fall deeper in love with You daily, desiring not to be conformed to this world, but transformed by the renewing of my mind with Your manna.

Help me to be a bold witness, to speak Your word, to be able to give an answer for the hope which is within me, saturate me with Your word, fill me fresh daily with Your presence, create in me a desire for You and the things of heaven.