If grace can't be merited, how does faith save you?

Lutero:

God's word isn't God's word because men say so but because God says so. There was always a church...that is an ekklesia which is the called out ones and this is not by man's doing but by the Holy Spirit. God doesn't change. Salvation has always been by grace through faith. Grace cannot be merited. For example, Abraham believed and it was credited to him as righteousness. Who credited righteousness to Abraham? A priest or God?

Now, if grace can not be merited, how does faith save you? Salvation is a grace, isn't it? Because you must first have faith in order to be saved. If you do not have faith you do not merit salvation. God doesn't give the gift of salvation to sinners. He gives the gift of faith to sinners who must then act upon that faith in order to be saved.

Hebrews 11:6

King James Version (KJV)
⁶ But without faith it is impossible to please him: for he that cometh to God must believe that he is, and that he is a rewarder of them that diligently seek him.

Sincerely,

De Maria