"But the Lord said to me, 'Do not say, "I am only a child." You must go to everyone I send you to and say whatever I command you. Do not be afraid of them, for I am with you and will rescue you,' declares the Lord." NIV translation
God reminds the prophet that he is not alone and so he is not "only a child". He is also told to not be afraid because God is in control and able to rescue him from his enemies. These same reminders apply to us as we serve the living God and He has never changed. This is also what God told the prophet Ezekiel when he was being prepared for service (see Ezekiel 2).
"Then the Lord reached out his hand and touched my mouth and said to me, 'Now, I have put my words in your mouth. See, today I appoint you over nations and kingdoms to uproot and tear down, to destroy and overthrow, to build and to plant.'" NIV translation
Now, the Lord reassures Jeremiah by touching him and telling him that it is God that will do the work and it will be His words. That is a good lesson for us as we seek to serve the Lord, our service must be by His Word and His power. Then, God tells him about his ministry and, at first glance, it seems to be all bad news as God says he is going to uproot and destroy. The last part tells of the fact that after the tearing down, he will be used to rebuild and the rebuilding will be on the foundation of God and not men. That, too, is a great lesson for us in our service to God in that it has to be based on the Word of God which is Jesus Christ. We, too, may have to tear down some false buildings and foundations but after that the rebuilding can begin on the solid Rock that is Jesus Christ.
"The word of the Lord came to me: 'What do you see, Jeremiah?' 'I see the branch of an almond tree,' I replied. The Lord said to me, 'You have seen correctly, for I am watching to see that my word is fulfilled.'" NIV translation
The Lord reassures Jeremiah with this vision of an almond branch. Almond trees grow wild in Israel and throughout the Bible they are used as a symbol of God's watchfulness over the affairs of His people. Almonds and their buds were on the candle holders that were made for the service of God (see Exodus 25). Aaron's rod was made of almond wood and Jacob used an almond branch to increase his flock (see Genesis 30). The almond tree is usually the first tree to sprout leaves in the spring and the last to lose them in the late fall. The Hebrew root of the word for almond is shaqed and the same root is used in the word shoqed which means to watch diligently. Sometimes, it is hard to say and do things that the Lord has for us to do and the same was true for the prophet here. We, like Jeremiah, can be comforted by the words of the Lord here and the fact that He is watching over us and His words.