Your questions: 1. Why if we are all supposed to be children of God and supposed to love one another, why did God allow people to own slaves in the Bible days? Even in the Old Testament, when God allowed many things of which he did not approve because of the hardness of their hearts (Matthew 19:8), the law demanded that slaves be treated with respect (Exodus 21:20-27) and in the first few verses of Exodus 21, we can see that in many cases slavery was simply a matter of “hiring out” services. Note Exodus 21:2, “If thou buy an Hebrew servant, six years he shall serve: and in the seventh he shall go out free for nothing.” Notice especially verse 7, “And if a man sell his daughter to be a maidservant, she shall not go out as the menservants do.” In the culture of the day a father had the right to “hire out” his daughter to be a maidservant, but notice in every case that there were restrictions that show that God never approved of what we normally think of as slavery, and when it was practiced, if his laws were obeyed, they would cause it to cease being practiced. As we have pointed out, even one statement of Jesus, if obeyed, would cause it to cease without warfare and social disturbance. In Ephesians 6:5-9, Paul recognized the fact that there were two kinds of servants–hired servants who were bound to do what they had contracted to do and servants who had been captured in war, or otherwise made slaves. He instructed both kinds to serve their masters the best they could, but was not thereby commending slavery.
Note carefully some things that Paul and others in the Bible said that indicates how God wanted the problem of slavery to be solved. When Paul sent Onesimus back to Philemon, he said to “treat him as a beloved brother” (Philemon1:16). He could not do that and maintain what was the usual human master-slave relationship.
When Paul in Galatians 3:28 said that “there is neither Jew nor Greek, slave or free” he was emphasizing that all are equal in the sight of God, and when a person recognizes this, if he is interested in doing things God’s way, he will treat all persons as he would like to be treated. In fact the very statement of Jesus in Luke6:31would fix that problem if it were obeyed. “And as ye would that men should do to you, do ye also to them likewise.” God permitted and still permits men to do many things that he does not approve of. There is nothing in the Bible that indicates that God ever approved of what we think of as slavery, although he did allow the Israelites to take captives in war those ungodly nations that had tried to destroy them.
Your second question: 2. The sixth commandment says do not kill, yet God gave Sampson, King David and others powers to kill. How is that? The word “kill” in that commandment simply means that they are not to murder. There is a great deal of difference in a person murdering another, and judicial punishment of killing or killing in time of war in defense of one’s country. God COMMANDED that persons be put to death for various crimes (Ex.21:12and various other places), but that was not contrary to his commandment not to murder. God has the right to condemn certain persons to die, and did so many times by the hand of his servants.
Your third question: 3. When we die, do we go directly immediately to heaven or hell, or just wait in the grave? Neither. The best answer to that question is probably found in Luke 16 in the story of the rich man and Lazarus. However, it still will not be clear to you unless you realize that all persons who die go into Hades (the realm of unseen spirits). Those who have done evil go into the part of Hades known as Tartarus (2 Peter 2:4). Those who have lived righteous lives go into the part known asParadise. Then on the Day of Judgment, the saved go on into heaven and the lost go into Gehenna (hell).