Linguistically, the direct object of give is the infinitive clause, with thee as the subject, and faithfully modifying to follow:
thee faithfully to follow
This statement is steeped in the theology of John Calvin. Born as a Puritan, Isaac Penington was influenced by John Calvin's teaching. The fourth principle of the Calvinist acronym, TULIP applies to this series of phrases:
The Lord lead thee as he seeth good, and give thee faithfully to
follow; for else, if the Lord should lead in any thing, and thou not
follow in that thing, his Spirit would be grieved and vexed thereby,
and thy heart in danger of being hardened by the deceitfulness of sin.
When God calls his elect into salvation, they cannot resist. God
offers to all people the gospel message. This is called the external
call. But to the elect, God extends an internal call and it cannot
be resisted. This call is by the Holy Spirit who works in the hearts
and minds of the elect to bring them to repentance and regeneration
whereby they willingly and freely come to God. Some of the verses used
in support of this teaching are Romans 9:16 where it says that "it is
not of him who wills nor of him who runs, but of God who has mercy";
Philippians 2:12-13 where God is said to be the one working salvation
in the individual; John 6:28-29 where faith is declared to be the work
of God; Acts 13:48 where God appoints people to believe; and John
1:12-13 where being born again is not by man’s will, but by God’s.
Pennington is praying that God will give his disciples both the internal and the external call.
- The prayer: [May] The Lord
- External call: lead thee as he seeth good
- Internal call: give thee faithfully to follow
- Explanation: for else, if the Lord should lead in any thing, and thou not follow in that thing, his Spirit would be grieved and vexed
thereby, and thy heart in danger of being hardened by the
deceitfulness of sin.
Those not steeped in Calvinist theology find it curious that God should have to fulfill his responsibility as well as ours. As Edwin Ashworth suggested, the phrase faithfully to follow could be replaced conceptually by the word grace:
The Lord lead thee as he seeth good, and give thee grace (the faithfully
It may be particularly perplexing that God should be vexed at our failure to follow, if he refused to give the internal call, but that is the intellectual foundation of Isaac Penington's statement.