Confidence is often attained by positive reinforcement along with successfully completing goals, tasks and feeling liked and accepted by peers and others.
With that in mind, I am not sure why you feel your son lacks confidence as you were not specific with any issues he may be going through which can affect self-confidence.
I state this as it may not be a lack of confidence you see but something else if there are concerns. As your son is a teenager, there are many feelings, emotions, and changes he is probably going through.
At this stage in development, young people are often trying to figure out who they are separate from their parents, and who they are in the larger sense of the world.
Young men are usually interested in girls, curious about sex, thinking about fitting in and being accepted by their peers as well as being liked by girls. While this is not in an Islamic context per say, it is to a degree as it is part of human nature.
Young men at this age are often thinking about getting good grades, going to a university in the future or getting a good job. Also of concern is being good at whatever hobby or interest they may have such as sports.
While you probably already know all of this I do mention it as a way of connecting confidence to the struggles he may be going through as well as peer pressure that often occurs around this age.
You can help him develop his confidence by understanding who he is, what he feels and respecting that person who he is, and who he hopes to be. Help him to understand his strengths and weaknesses and to know that to fail in a task (as we all do) is a learning experience so we can try again.
Teach him to be proud (but not arrogant) of his gifts and abilities, and that to work on one’s weaknesses is a sign of strength and determination.
Tell him often you are proud of him. Ask him frequently how he is progressing on a goal to show it is of value and that you are interested. Set him up for success. Once you know his strengths, encourage him to pursue them.
If he is good at sports, have him join a sports team. If speaking and articulating is his thing, encourage him to join a debate team.
Nurture his abilities and respect his choices. If he is interested in something you do not like, don’t downgrade it, but support it as it is his choice.
Keep the lines of communication open so that he feels confident to talk to you about anything! Young men tend to open up better when engaged in conversation while doing a task. Find something he enjoys doing and use this time for in-depth communication.
This goes back to the above possible interests such as sex, girls, fitting in, peer pressure, career choices, among other things. Make sure he knows he can talk to you about these things without fear of judgment or rejection.
While you do want to provide good Islamic advises, you also need to be his friend in addition to being his parent.
Young people who feel they can talk to their parents about anything that is bothering them and receive supportive, kind responses, statistically tend to have higher confidence levels.
This is not to say to be supportive of haram goals or behaviors but it is saying to listen, be there and offer Islamically based problem-solving skills to aid him in making wise decisions if he comes to you with a problem.
Along with encouraging communication, insha’Allah respect his emotions as well and do not try to make him feel “less than a man” should he express sensitive emotions or feel like crying over something that has hurt him. Allow him to be fully human.
Check out this counseling video
Give your son increasing responsibility. This can range from adding more chores, letting him drive the family car, giving him a special project to work on such as building a fire-pit for BBQ’s to taking care of a family member who may be sick or in need.
Praise him for his accomplishments concerning these increased responsibilities, pointing out the successes resulting from his efforts. If he is able (working part time or begins to work) encourage him to begin to pay some of his bills such as his cell phone.
This not only boosts confidence in an ability to manage his money but also gives him a sense of empowerment as a young adult who is taking responsibility for his own needs. Engage him in charitable works in the Islamic community.
Not only will helping others give him a sense of accomplishment, but it will also insha’Allah, help keep him humble, and grateful for his blessings. It will also be an opportunity for him to make lasting friendships with others. As he is an only child, this will be especially important.
Lastly, model confidence! As his parent, he looks to you as a role model. If you are insecure about yourself, he will pick up on it. Don’t always put yourself down, or express self-doubt all the time.
While we all have areas we need to improve in, use these as teaching points of how to “get back up and try again”. Be willing to try new activities, this will illustrate to your son that new things are not always scary and seeing you try new things will give him the confidence to do so as well.
Insha’Allah these tips have helped, it sounds as if you already are on the way to raising a wonderful and confident son as you took the time and concern to ask!