What the free grace position simply will not allow is that the change produced by regeneration is the grounds of or the evidence for assurance of genuine salvation. (Thomas G. Lewellen, “Has Lordship Salvation Been Taught Throughout Church History?” 65.)
This is the most important sentence in that statement, and what it is all about.
Free Grace believers depend on scripture and God's promises for assurance. I came to Jesus in my heart and called upon him to save me, therefore I can claim many direct promises made in scriptures such as John 6:37 and Romans 10:13;
Jhn 6:37 All that the Father giveth me shall come to me;
and him that cometh to me I will in no wise cast out.
Rom 10:13 For whosoever shall call upon the name of the Lord shall be saved.
Free Grace persons like me will claim these and other verses as scriptural proof we are saved. I know that in my heart I came to Jesus and sincerely called upon him to save me, and so I can claim the direct promises of God in scripture as my assurance of salvation.
As Curtis Hutson used to say, "If I am not saved, God will lose more than me. I will simply lose my soul, but God will lose his integrity".
I am not depending on my performance or faithfulness to Jesus as my security and assurance of salvation, I am completely depending on Jesus's perfect faithfulness to me to keep his promise to save me if I came to him.
Lordship Salvation is the exact opposite, it expects faithfulness from the believer as his security and assurance of salvation. Unless he is doing a reasonable job of obeying Jesus, he can have no assurance or guarantee of salvation. The problem is, no Lordship Salvation person can tell you how obedient you must be to prove you are saved.
But they are not the same as that author seemed to argue. Free Grace and Lordship Salvation are direct opposites.
Free Grace- depends on Jesus's faithfulness
Lordship Salvation - depends on the believer's faithfulness.
One is scriptural, one is not.