Augustine of Hippo — on Rom 8:26 (AUGUSTINE ON ROMANS 54)

“It is clear from what follows that Paul is speaking here about the Holy Spirit.… "We do not know how to pray as we ought" for two reasons. First, it is not yet clear what future we are hoping for or where we are heading, and second, many things in this life may seem positive but are in fact negative, and vice versa. Tribulation, for example, when it comes to a servant of God in order to test or correct him may seem futile to those who have less understanding.… But God often helps us through tribulation, and prosperity, which may be negative if it traps the soul with delight and the love of this life, is sought after in vain.The Spirit sighs by making us sigh, arousing in us by his love a desire for the future life. "The Lord your God tempts you so that he might know whether you love him," that is, to make you know, for nothing escapes God's notice.”