Every interaction with another person holds the potential for unity. How can that be? Let’s let the author of Bilvavi explain it:
The power of giving can unite a person with all of creation. We may not, G-d forbid, unite with the evil manifestation of anything, but we can unite with the hidden good in all of creation. There is no created being in the world without some spark of goodness. If it did not have a spark of goodness, it would not be able to exist.
Hence, when one gives properly and in the proper place, it engenders unity. The Talmud (Ketubot 105b) states that the word shochad (a type of giving) is a contraction of shehu chad (becoming one), because the giver and taker become one. Superficially, a person thinks, “I gave to that person. That was good, but now, it’s over. I had the thing and then gave it a way. The act took a minute or two, and then we went on our separate ways.” But in depth, as Chazal teach, they become one.
If I gave a carton of milk to a neighbor from downstairs who needed it, or I met someone in the bus station who needed money for bus fare, and I handed him nineteen shekalim, do I become one with him? How can such trivial acts unify people? If one wants to unite, as with a spouse, it is a process of years, as we all know. How can a minor act unify people?
Here is the answer: If you take a magnet and place it next to another one, they will become attached to each other. But if something else is placed between them, they will not be able to join. The moment the intervening item is removed, they will naturally join. This is the deep condition of all of creation. If we would try to create a new unity where one never existed, it would be difficult, and in fact, impossible. But the natural state of people is to be one. All of our souls were contained in Adam HaRishon. There, we were one person. Afterwards, we became more and more divided from each other, until coming to our current state. Unity is not a new state; it is a return to the primal state.
There is a divider that separates us, namely, the body, which has a desire to take, but once one removes that will to take, he will sense a natural unity with other people. If the natural state of people is to be absolutely separate, the avodah to unite them would be very difficult and actually impossible. But since they are essentially one, but each person later fashions his own will and his own concerns and an attitude of taking, there is a separation caused between people. After we have removed this desire to take, and have acted upon the loftier desire by really giving, there is no real need to “create” unity. You must understand this, because it is subtle and deep. Giving, in depth, does not unite; it removes the cause of separateness. After the cause of separateness has been removed, we naturally unite.
From the third volume of Bilvavi, Da Es Atzmecha – Know Yourself which can be read online here.