Listening to the word of the Lord is more important than sacrificing to the Lord

1 Samuel 15:1-16

This is what the Lord Almighty says: ‘I will punish the Amalekites for what they did to Israel when they waylaid them as they came up from Egypt. Now go, attack the Amalekites and totally destroy all that belongs to them. Do not spare them; put to death men and women, children and infants, cattle and sheep, camels and donkeys.’”

But Saul and the army spared Agag and the best of the sheep and cattle, the fat calves[b] and lambs—everything that was good. These they were unwilling to destroy completely, but everything that was despised and weak they totally destroyed.

Then the word of the Lord came to Samuel: “I regret that I have made Saul king, because he has turned away from me and has not carried out my instructions.” Samuel was angry, and he cried out to the Lord all that night.

Saul answered, “The soldiers brought them from the Amalekites; they spared the best of the sheep and cattle to sacrifice to the Lord your God, but we totally destroyed the rest.”

Why?
Listening to the word of the Lord is more important than sacrificing to the Lord. Our Lord does not lack anything even the sacrifice. 

v 29 Also, the strength of Israel will not lie nor repent: for he is not a man, and he should repent.

Here the Lord said to Samuel: "I regret that I have made Saul king", This is described as a man who has the emotion to mention this issue. The Lord felt sad that the Lord chose Saul as a king.

Serve the Lord and honor God's Holy name is obeying God's commands. Others how much devotion, and how many times worship the Lord are not important.

How?

We are chosen by the Lord and should do our best to serve the Lord and obey the word of the Lord, for God's love endures forever.