Musar su Salmi 119:109

You should know that a handshake is also like an oath. For the soul is dependent upon the palm of the hand to its benefit as well as its detriment. It is dependent upon it to its benefit when a person raises his hands Heavenward to invoke mercy. Moreover, a high percentage of the mitzvos are performed by the hand, including: performing circumcision, offering a sacrifice, separating off the priestly and Levitical gifts, constructing a Sukkah, taking the four species, giving charity, donning tefillin and many others. These are just some of the ways in which the soul is dependent upon the hand. This is what King Dovid meant when he said, “My soul is in my palm continually and I have not forgotten Your Torah” (Tehillim 119:109). That is, I have chosen to use my hands for good purposes and not the opposite, Heaven forbid.