In the Old Testament God required many different sacrifices and offerings from both the people and the priests. Some were required daily, some weekly, some monthly, and some yearly (see for example Lev 1-7; Num 28-29). These offerings and sacrifices would have taken both a financial toll on the people as well as a physical toll, as the Temple in Jerusalem was the only authorized place to present offerings to God. From north to south Israel is about 150 miles, and from east to west spans approximately 75 miles. Jerusalem sits in the southern part of Israel. Thus traveling to Jerusalem to offering a sacrifice would have been no small task. Nonetheless, sacrifices and offerings were the means of worship which God had prescribed in the Old Testament, and a way in which one could demonstrate their devotion to God--a way of suffering for the Lord. In fact, the word sacrifice by definition implies the suffering of loss.
However, the simple act of presenting offerings and sacrifices to the Lord was never enough for God. In the Old Testament, the attitude of the heart in the giving of the offering or sacrifice was just as important to God, if not more. Of course Cain is the first and classic example to illustrate this point. There in Genesis 4 we read: “ In the course of time Cain brought to the LORD an offering of the fruit of the ground, and Abel also brought of the firstborn of his flock and of their fat portions. And the LORD had regard for Abel and his offering, but for Cain and his offering he had no regard” (vv. 3-5). Notice the text says that Cain brought to the Lord “an offering of the fruit of the ground”. Yet with regards to Abel's offering we are told that he brought “of the firstborn of his flock”. It's not so much that Abel brought something better, and it's not that God prefers sheep or goats over fruits and grain—this is clear from the fact that God prescribes the use of grain offerings in Leviticus 2—rather it has to do with the attitude of the heart in the giving of the offering. It may be that they both thought that giving something to God would be costly and difficult, a suffering of loss, thus Cain sought to minimize his suffering by offering something less costly. Yet by the very act of doing so he was murmuring against that which God had willed for his life at that moment.
We see a similar event in 1 Samuel 15 where King Saul had been commanded by God to utterly destroy the Amalekites, “both man and woman, child and infant, ox and sheep, camel and donkey” (v.3). Yet Saul decides to spare the “best of the sheep and of the oxen and of the fattened calves and the lambs, and all that was good” (v. 9). When Saul tries to explain that he had brought the best of what the Amalekites possessed so that he might offer them to God, Samuel replies: “Has the LORD as great delight in burnt offerings and sacrifices, as in obeying the voice of the LORD? Behold, to obey is better than sacrifice, and to listen than the fat of rams” (v. 22). We cannot miss the point that the issue is not merely about obedience vs. disobedience, but is about the heart attitude that causes obedience or disobedience. Obedience stems from a heart that desires to honor God, that trusts God, that believes his word even when it doesn't make sense to do so. Disobedience stems from a heart that lacks confidence in God, that does not fully trust God, and questions the wisdom of God. In the end, Saul's biggest problem was a heart issue--not simply an obedience issue.
The problem is magnified by the late 5th century BC when we see in Malachi chapter 1 that God will reject the offerings of the people because they are despising God's name. “But you say, 'How have we despised your name?' By offering polluted food upon my altar. But you say, 'How have we polluted you?' By saying that the LORD's table may be despised. When you offer blind animals in sacrifice, is that not evil? And when you offer those that are lame or sick, is that not evil?” Again it cannot be missed that the issue here is not simply a disregarding of Old Testament law, but a heart issue that leads to that disregard. This is the very issue that Jesus would later condemn the Pharisees about in Matthew 15. “Well did Isaiah prophesy of you, when he said: 'This people honors me with their lips, but their heart is far from me; in vain do they worship me'” (vv. 7-9). Regardless of the sacrifices and offerings they would present to God, their worship was in vain because their hearts were far from Him.
In Romans 12:1-2 the apostle Paul makes clear that worship for God is not just singing, and it's not just what we do on Sunday mornings, worship is how we live and think and and feel and what we believe. Worship is the whole of who we are and what we do. Thus, just as worship in the Old Testament, which entailed the suffering of loss through costly sacrifices and offerings, was accepted by God, and was glorifying to God when rendered from a heart that desires to honor God, that trusts God, and believes his word. So also when we experience suffering in this life by the foreordained will of God, we offer acceptable worship to God when we endure suffering with a heart that desires to honor him, that trusts him, and believes his word. When we murmur about the suffering which God has called us to walk through, while simultaneously attending church and engaging in other Christian activities, we become like Cain and the Jews of old who suffered the loss of sacrifices and offerings--halfheartedly. It is for this reason James writes that we should “count it all joy, my brothers, when you meet trials of various kinds, [knowing] that the testing of your faith produces steadfastness” (1:2-3). Or, that Paul could write “we rejoice in our sufferings” (Rom 5:3). When we endure sufferings with joy, with confidence in God, with a heart that fully believes God is working all things for our good and for his glory (Rom 8:28), we render to God acceptable, glorifying, honoring worship.