The context of this prayer, which comes at the end of Lecture 6 on Jeremiah, is the unreasonableness and illogicality of God’s people turning from all his kindness and grace toward them and relying on their own devices – “..my people have committed two evils: they have forsaken me, the fountain of living waters, and hewed out cisterns for themselves, broken cisterns that can hold no water.” (Jeremiah 2:13).
“Grant, Almighty God, that as thou hast hitherto shewn to us so many favours, since the time thou hast been pleased to adopt us as thy people, – O grant, that we may not forget so great a kindness, nor be led away by the allurements of Satan, nor seek for ourselves inventions, which may at length turn to our ruin; but that we may continue fixed in our obedience to thee, and daily call on thee, and drink of the fulness of thy bounty, and at the same time strive to serve thee from the heart, and to glorify thy name, and thus to prove that we are wholly devoted to thee, according to the great obligations under which thou hast laid us, when it had pleased thee to adopt us in thine only-begotten Son. Amen.
(Commentary on Jeremiah, vol 1, p106
Edinburgh: Banner of Truth Trust, 1989)