I can't speak for him or anyone, but what he did I'm sure he wanted nothing in return. Kind acts as you call them are definitely needed in this world. It is something I think a lot of the world has forgotten about. As cities grow and populations burst many times it becomes all about the money to some people. I have always lived by the philosophy give and it is given back. It is more of unliteral sense, because you don't actually expect the same to happen or something in the same form to happen. You just know and feel that something good will happen to you, because you made someone else have that feeling of joy and happiness. It is something everyone needs to think about. If everyone stopped and cared enough for each other than think of the how problems of this world could be solved.

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Edit:
I originally just responded to the idea, but there are many times when I have given and also have been given too. Infact just recently I had been weighing on wither or not to sell some College Football Tickets I have had, but really didn't want to go. A man that works in the warehouse where I pick up my DFI's, or basically packages I deliver to businesses with my job, has a daughter and he mentioned how he wished he could go see one Razorback game with her, but he had never had the money to get tickets as they are worth $55 each. When I heard about it I really thought that it'd be better I gave them than to sell them. I figured why not bless a man with something he has been wanting than sell them for really no profit at all. Of course I could really only give him my ticket, but I talked with my dad about him giving his ticket since he wasn't going either. My dad agreed and thought it would really be a good thing to do. So I gave my ticket along with my dad's ticket to the man. Was he ever happy he almost started crying. He shook my hand and said "Thank you so much." As I was about leave he ran up to catch me and to my surprise gave me a hug. I guess it goes to show that he really was thankful for those tickets.