Markus 10:38

10:38 But Jesus said to them, “You don’t know what you are asking! Are you able to drink the cup I drink or be baptized with the baptism I experience?” ¹ 

Roma 8:26

8:26 In the same way, the Spirit helps us in our weakness, for we do not know how we should pray, ²  but the Spirit himself intercedes for us with inexpressible groanings.

Yakobus 4:3

4:3 you ask and do not receive because you ask wrongly, so you can spend it on your passions.

¹ tn Grk “baptism I am baptized with.” This same change has been made in v. 39.

² tn Or “for we do not know what we ought to pray for.”