Luke 7:44-50 KJV
And he turned to the woman, and said unto Simon, Seest thou this woman? I entered into thine house, thou gavest me no water for my feet: but she hath washed my feet with tears, and wiped them with the hairs of her head.
Thou gavest me no kiss: but this woman since the time I came in hath not ceased to kiss my feet.
My head with oil thou didst not anoint: but this woman hath anointed my feet with ointment.
Wherefore I say unto thee, Her sins, which are many, are forgiven; for she loved much: but to whom little is forgiven, the same loveth little.
And he said unto her, Thy sins are forgiven.
And they that sat at meat with him began to say within themselves, Who is this that forgiveth sins also?
And he said to the woman, Thy faith hath saved thee; go in peace.
Scofield's Notes are helpful here,
"When Jesus would justify the woman in the eyes of Simon, He points to her works, for only through her works could Simon see the proof of her faith; but when He would send the woman away in peace, He points to her faith, not her works.
His own works can never be to the believer his own ground of assurance, which must rest upon the work of Christ. "
On the subject of assurance of salvation, the only way an outsider can tell if a person is saved is by observing what they do, their works. However, when dealing with a person concerning their own salvation only one thing matters, their faith.
Personal assurance cannot and must not be built upon our own works for surely they ebb and flow and they would place our trust on ourselves instead of Christ. True assurance comes when we have heard the voice of the Holy Spirit testify to our own spirit that we are a child of God.