Markus 2:21

2:21 No one sews a patch of unshrunk cloth on an old garment; otherwise, the patch pulls away from it, the new from the old, and the tear becomes worse.

Markus 9:18

9:18 Whenever it seizes him, it throws him down, and he foams at the mouth, grinds his teeth, and becomes rigid. I asked your disciples to cast it out, but ¹  they were not able to do so.” ² 

Markus 16:14

16:14 Then he appeared to the eleven themselves, while they were eating, and he rebuked them for their unbelief and hardness of heart, because they did not believe those who had seen him resurrected.

[9:18]  ¹ tn Here καί (kai) has been translated as “but” to indicate the contrast present in this context.

[9:18]  ² tn The words “to do so” are not in the Greek text, but have been supplied for clarity and stylistic reasons.