These two church members apparently did not take Satan into consideration. They listened to a lie and were divided, first, from God's church and then from life itself. What did Satan do? He moved them toward self-satisfaction to the point (the actual sin) that they lied to take credit for a greater sacrifice than they actually made.
The sad part of this is that no one asked them to donate the entire sale price of the piece of land. What happened was they committed themselves to it and then undoubtedly began to feel put on. "Hey, Sapphira, that's too much money." Maybe they began to think, "We didn't expect we'd get so much money from the sale of this, and it is too much to donate." They began to think, undoubtedly, of other uses that they could put the money to. "We could buy new clothes. We could improve the house. We could buy another piece of land as an investment and make even more from it."
They had apparently already told those who were in charge of the collection that they would contribute the entire amount of the sale, and when the time came to give the contribution, they gave only a part of it but let on as if it was the entire sale price. They kept the difference for themselves.
Who led them to dare to lie? Satan has a modus operandi. He will always move us in the direction of self-satisfaction at the expense of obedience to God, service to God, or service to others, so that we elevate ourselves over the others.
Is that not what Satan did originally? In his own mind, his vanity elevated him higher than the position God had given to him, and it then began to work on his mind so that he had to do something about it. This process repeats itself over and over again.