9 How can a young person stay on the path of purity?
By living according to your word.
10 I seek you with all my heart;
do not let me stray from your commands.
11 I have hidden your word in my heart
that I might not sin against you.
12 Praise be to you, Lord;
teach me your decrees.
13 With my lips I recount
all the laws that come from your mouth.
14 I rejoice in following your statutes
as one rejoices in great riches.
15 I meditate on your precepts
and consider your ways.
16 I delight in your decrees;
I will not neglect your word. 
Psalm 119 is an acrostic based on the 22 letters of the Hebrew alphabet. The first word of each line in each section starts with the Hebrew letter for that section. In so many ways it is a beautiful piece of poetry. Some attribute this Psalm to David, but the text doesn’t preserve who the author actually is, and it probably isn’t necessary to know. What is important is the one theme that runs throughout the entire Psalm. That theme is the word of God! Many terms are used, like commands, word, judgments, statutes, etc. All of those words reference the word of God. If you have time, don’t just read the verses I posted, read the entire thing.
Here is what the prince of preachers Charles Spurgeon says about this Psalm, “The one theme of this Psalm is the word of the Lord. The Psalmist sets his subject in many lights, and treats of it in divers ways, but he seldom omits to mention the word of the Lord in each verse under some one or other of the many names by which he knows it; and even if the name be not there, the subject is still heartily pursued in every stanza.”
The question in verse 9 is so important, “How can a young person stay on the path of purity?” Perhaps that question shouldn’t be limited to young people. All people need to remain on the path of purity, but it is especially hard and important to young people. God’s word is valuable to teach, correct, and guide, among other things (see 2 Timothy 3:16). We see all of those things in this Psalm.
What does it mean to “hide God’s word in your hearth?” Many will use this verse to suggest that we need to memorize God’s word, that is a reasonable conclusion, but it is really more than that. Memorizing God’s word allows us to take it with us in a way that simply reading it does not. However, there is s sense of internalizing it that must go along with memorization. If we memorize it we can meditate on it, recall it, and use it to minister and witness to others. Further, we are more able to be obedient to God, make right judgments about the world, and live in obedience to God.
You can do it, memorize one verse this week. Write it down on a note card and put it somewhere where you will see it and read it. Do it as a family. Perhaps you will start with something really common like John 3:16 or maybe you will look at something like Isaiah 5:20. Pick a verse and memorize it, but do more than that and begin to allow it to change you.
 The New International Version (Grand Rapids, MI: Zondervan, 2011), Ps 119:9–16.
 Charles Haddon Spurgeon, The Golden Alphabet: A Devotional Commentary on Psalm 119 (WORDsearch, 2007), 12.