Why does the New Testament at times describe the cross as a tree?

Serving Sodom's king or Salem's King? | Genesis 14

Coming to see Jesus for who he really is | Luke 5:1-11

A warning and an encouragement | Genesis 13

“The point of the story of Abram in Egypt is simply that God’s plan and his promises will come to pass, even though humans are sinful and weak” | Genesis 12:10-13:4

A Second Adam to the fight and to the rescue came | Luke 3:21 - 4:13

The life of Abraham is more than just an example - he plays a unique role in God's plan of salvation. And yet he is also a great example of faith, trusting the bare word of God, and worshipping God whatever those around him are doing | Genesis 12:1-9

“People are ruined, not so much by what they do, but because they don’t repent” - Matthew Henry

Abraham is mentioned in the first verse of the New Testament. If we don't understand him, we won't understand Jesus | Genesis 11:27-32

What do we learn from the first recorded words of Jesus? | Luke 2:41-52