"The prayer of the sick for himself will avail more than any other. " ~~ Genesis (Bereshit) R.
"All are equal in prayer before the Lord. " ~~ Exodus (Shmot) R.
"Any study of the Torah and any prayer unaccompanied by good deeds and repentance void the Torah and make the prayer unwanted." ~~ Otiyot Derabbi Akiva
"The best weapons of Jew are his prayers." ~~ Nachman of Bratslav
"But how can you say, “It was only talk, so no harm was done?” Were this true, then your prayers, and your words of kindness, would be a waste of breath." ~~ Nachman of Bratslav
"Who prays in Jerusalem is as one praying before the Throne of Glory, for the Gate of Heaven is there." ~~ Pirke Derabbi Eliezer
"Eating is the best of prayers." ~~ Avrunin
"Music is prayer. " ~~ Ludwig Boerne
"Repentance is valued above sacrifices [Pesikta R.]… above prayer." ~~ Tanna Deve Eliyahu Zuta
"Pray for the peace of Jerusalem!" ~~ Psalms (Tehillim) 122:6
"The gates of prayer are never closed. " ~~ Deuteronomy (Devarim) R.
"Who answers Amen is greater than the suppliant." ~~ Talmud, Berakhot