'Attesting' in the Bible

Now formerly in Israel this was the custom concerning redeeming and exchanging property. To confirm a transaction, a man pulled off his sandal and gave it to the other. This was the way of confirming and attesting in Israel.

Now the Pharisees and Sadducees came up, and testing Jesus [to get something to use against Him], they asked Him to show them a sign from heaven [which would support His divine authority].

The Pharisees came out and began to argue [contentiously and debate] with Him, demanding from Him a sign from heaven, to test Him [because of their unbelief].

These signs will accompany those who have believed: in My name they will cast out demons, they will speak in new tongues;

And they went out and preached everywhere, while the Lord was working with them and confirming the word by the signs that followed.]