From: 'St. Peter's - Guide to the Basilica and Square'
Passing from the transept to the left aisle, on the left is the Altar of Ananias and Sapphira or Altar of the Lie. The mosaic is after a painting by Cristoforo Roncalli, known as Pomarancio (1552-1626), and shows the punishment of the couple who had lied to St. Peter.

From: Seminarians Guide
This altarpiece depicts the story in the Acts of the Apostles of the couple punished for withholding money that they had promised to the apostles and for lying to St. Peter. It is purposefully placed in front of the priest as he leaves the sacristy to celebrate Mass, a permanent reminder to him that he is called to give himself entirely to God and be a servant to His people, and woe to the priest who selfishly withholds from his promise!

From: 'St. Peter's Basilica - A Virtual Tour' by Our Sunday Visitor
Returning to the Michelangelo Ambulatory, on the inside wall is the Altar of the Lie, so called because of its mosaic altarpiece. It shows the sacrilegious fraud committed by Ananias and his wife Sapphira, who lied to St. Peter about the price of a field sold by them, and were therefore immediately struck dead. It was executed in 1768 by P. Adami from an original by C. Roncalli, with less than satisfactory results because the colors are too vivid.

Acts 5:1-11
1 Now a man named Ananias, together with his wife Sapphira, also sold a piece of property. 2 With his wife’s full knowledge he kept back part of the money for himself, but brought the rest and put it at the apostles’ feet. 3 Then Peter said, “Ananias, how is it that Satan has so filled your heart that you have lied to the Holy Spirit and have kept for yourself some of the money you received for the land? 4 Didn’t it belong to you before it was sold? And after it was sold, wasn’t the money at your disposal? What made you think of doing such a thing? You have not lied to men but to God.” 5 When Ananias heard this, he fell down and died. And great fear seized all who heard what had happened. 6 Then the young men came forward, wrapped up his body, and carried him out and buried him. 7 About three hours later his wife came in, not knowing what had happened. 8 Peter asked her, “Tell me, is this the price you and Ananias got for the land?” “Yes,” she said, “that is the price.”9 Peter said to her, “How could you agree to test the Spirit of the Lord? Look! The feet of the men who buried your husband are at the door, and they will carry you out also.” 10 At that moment she fell down at his feet and died. Then the young men came in and, finding her dead, carried her out and buried her beside her husband. 11 Great fear seized the whole church and all who heard about these events.