Is shaking the hand during a handshake a condition for sins to fall away?

It is from the Sunnah for a Muslim to shake hands with his Muslim brother when they meet. It has been reported that this expiates their sins, and there is no mention of the necessity of shaking the hand for forgiveness. The Prophet, peace and blessings be upon him, said: "Indeed, when a Muslim shakes hands with his brother, their sins fall away, just as the leaves of a tree fall." He also said: "When a believer meets another believer, greets him with salaam, takes his hand, and shakes it; their sins fall away, just as the leaves of a tree fall."