Summary: God always plans things so that we will have the chance to witness about Jesus. We have to be open to these chances. We must always be ready to witness about Jesus. To do so, we must be familiar with God's Word.
The reading from 1 Samuel 13:5-18 shows what happens when we disobey God. King Saul was told to wait and let the prophet Samuel make the burnt offerings to God. Instead, King Saul made the burnt offering himself.
Here's the situation. The Philistines and Israelites were at war. The Philistine army, which numbered at least 36,000 men, was assembled on the Philistine plain. Now that must have been a frightening sight for the Israelites because most of them fled into caves. Saul got tired of waiting for Samuel, so he made the burnt offering.
King Saul wanted to gain the glory of victory for himself instead of giving it to God. Needless to say, by the time Samuel finally arrived and found out what Saul did, he was not happy. We, like King Saul, are tempted to take matters into our own hands when things go wrong. We, like King Saul, must remember that God is in control and we need to obey God at all times. King Saul's punishment for his disobedience was the eventual loss of his position of king to David. King Saul failed to acknowledge Samuel's role as the divine messenger. In other words, King Saul failed to listen to the word of God.
God saw that David had a heart for God. That heart was sensitive to the things of God. God looks for people whose hearts are completely his. That includes obeying the word of God, regardless of who we hear it from-either from God directly or through his messengers.
In contrast to King Saul, Philip obeyed God. The angel of the Lord told Philip to go to the Ethiopian eunuch. Philip explained the content of the Book of Isaiah to the Ethiopian. Philip obeyed when the Ethiopian wanted to be baptized. When he did everything he was asked to do, the angel of the Lord took Philip to the place where Philip originally wanted to go.
By being receptive to the Holy Spirit, we, like Philip, can find guidance from God for our daily choices and decisions. Philip didn't know that God had planned to use the Ethiopian to be the first preacher of the Gospel in Ethiopia (according to tradition). Philip's message was tailored to the Ethiopian, just like I have tailored my message to you. Philip was guided by the Holy Spirit's concern for people. Philip saw that the Ethiopian was interested in the Scriptures.
The late Beatle John Lennon once said that "life is what happens to you when you're busy making other plans". We are going in one direction for one reason or another when something significant happens that changes our plans. That event could be anything from a meeting or a conversation that has an impact on someone else's life. Just look at the apostle Paul for example. He was on his way to Damascus to arrest Christians and bring them back to Jerusalem for trial when he quite literally saw the light of Christ. That encounter changed his life. Instead of being a zealous persecutor of Christians, he became a zealous spreader of the Good News. In fact , if it wasn't for the work of Paul and his helpers such as Timothy and Silas, Christianity would not have had the impact that it did, and Christianity would not have the impact that it still has today.