2 Chronicles 12:14
And he did evil because he did not set his heart to seek the LORD.

It was not a deliberate evil but the result was evil because he was not seeking God. You can't be walking with God if you aren't seeking!

It cannot be more clear that God will reveal Himself to us if we seek Him:

2 Chronicles 15:2
and he went out to meet Asa and said to him, "Listen to me, Asa, and all Judah and Benjamin: the LORD is with you when you are with Him. And if you seek Him, He will let you find Him; but if you forsake Him, He will forsake you.

2 Chronicles 15:4
"But in their distress they turned to the LORD God of Israel, and they sought Him, and He let them find Him.

2 Chronicles 15:15
And all Judah rejoiced concerning the oath, for they had sworn with their whole heart and had sought Him earnestly, and He let them find Him. So the LORD gave them rest on every side.

2 Chronicles 16:9
"For the eyes of the LORD move to and fro throughout the earth that He may strongly support those whose heart is completely His. You have acted foolishly in this. Indeed, from now on you will surely have wars."

2 Chronicles 30:18-19
18 For a multitude of the people, even many from Ephraim and Manasseh, Issachar and Zebulun, had not purified themselves, yet they ate the Passover otherwise than prescribed. For Hezekiah prayed for them, saying, "May the good LORD pardon 19 everyone who prepares his heart to seek God, the LORD God of his fathers, though not according to the purification rules of the sanctuary."

Psalm 105:3-4
3 Glory in His holy name; let the heart of those who seek the LORD be glad. 4 Seek the LORD and His strength; seek His face continually.

We don't seek Him in vain:

Isaiah 45:18-22
18 For thus says the LORD, who created the heavens (He is the God who formed the earth and made it, He established it and did not create it a waste place, But formed it to be inhabited), "I am the LORD, and there is none else. 19 "I have not spoken in secret, in some dark land; I did not say to the offspring of Jacob, `Seek me in a waste place'; I, the LORD, speak righteousness declaring things that are upright. 20 "Gather yourselves and come; draw near together, you fugitives of the nations; they have no knowledge, who carry about their wooden idol, and pray to a god who cannot save. 21 "Declare and set forth your case; indeed, let them consult together. Who has announced this from of old? Who has long since declared it? Is it not I, the LORD? And there is no other God besides me, a righteous God and a Savior; there is none except me. 22 "Turn to me, and be saved, all the ends of the earth; for I am God, and there is no other.

Isaiah 55:6-12
6 Seek the LORD while He may be found; call upon Him while He is near. 7 Let the wicked forsake his way, and the unrighteous man his thoughts; and let him return to the LORD, and He will have compassion on him; and to our God, for He will abundantly pardon. 8 "For My thoughts are not your thoughts, neither are your ways My ways," declares the LORD. 9 "For as the heavens are higher than the earth, so are My ways higher than your ways, and My thoughts than your thoughts. 10 "For as the rain and the snow come down from heaven, and do not return there without watering the earth, and making it bear and sprout, and furnishing seed to the sower and bread to the eater; 11 So shall My word be which goes forth from My mouth; it shall not return to me empty, without accomplishing what I desire, and without succeeding in the matter for which I sent it. 12 "For you will go out with joy, and be led forth with peace; the mountains and the hills will break forth into shouts of joy before you, and all the trees of the field will clap their hands.

Seek the Lord while He may be found. God's word will not return empty.

[1.] it is implied that now God is near and will be found, so that it shall not be in vain to seek him and to call upon him. Now his patience is waiting on us, his word is calling to us, and his Spirit striving with us. Let us now improve our advantages and opportunities; for now is the accepted time. But, [2.] There is a day coming when he will be afar off, and will not be found, when the day of his patience is over, and his Spirit will strive no more. There may come such a time in this life, when the heart is incurably hardened; it is certain that at death and judgment the door will be shut. Mercy is now offered, but then judgment without mercy will take place. (from Matthew Henry's Commentary)

Luke 13:23-28
23 And someone said to Him, "Lord, are there just a few who are being saved?" And He said to them, 24 "Strive to enter by the narrow door; for many, I tell you, will seek to enter and will not be able. 25 "Once the head of the house gets up and shuts the door, and you begin to stand outside and knock on the door, saying, `Lord, open up to us!' then He will answer and say to you, `I do not know where you are from.' 26 "Then you will begin to say, `We ate and drank in Your presence, and You taught in our streets'; 27 and He will say, `I tell you, I do not know where you are from; depart from Me, all you evildoers.' 28 "There will be weeping and gnashing of teeth there when you see Abraham and Isaac and Jacob and all the prophets in the kingdom of God, but yourselves being cast out.

Going to church and bible studies doesn't do it. These people ate and drank in God's house but they didn't know God. You can try to act as good as you want, that is not what matters. The HEART must be seeking God! It's a conscious effort to seek the Lord.

Ezekiel 33:31-33
31 "And they come to you as people come, and sit before you as My people, and hear your words, but they do not do them, for they do the lustful desires expressed by their mouth, and their heart goes after their gain. 32 "And behold, you are to them like a sensual song by one who has a beautiful voice and plays well on an instrument; for they hear your words, but they do not practice them. 33 "So when it comes to pass-- as surely it will-- then they will know that a prophet has been in their midst."

Matthew 7:7-8
7 "Ask, and it shall be given to you; seek, and you shall find; knock, and it shall be opened to you. 8 "For everyone who asks receives, and he who seeks finds, and to him who knocks it shall be opened.

Now are those old testament verses from above good for teaching, for guiding our life?

2 Timothy 3:16-17
16 All Scripture is inspired by God and profitable for teaching, for reproof, for correction, for training in righteousness; 17 that the man of God may be adequate, equipped for every good work.

Question:	Why is it necessary to have faith in God?
Answer:	And without faith it is impossible to please Him, for he who comes to God must believe that He is, and that He is a rewarder of those who seek Him. Hebrews 11:6