…his father saw him, and was moved with compassion, and ran, and fell upon his neck, and covered him with kisses. – Luke 15:20

The father kissed his son much to make him quite certain that it was all real. The prodigal, in receiving these many kisses, might say to himself, “All this love must be true, for a little while ago I heard the hogs grunt, and now I hear nothing but the kisses from my dear father’s lips.” So his father gave him another kiss, for there was no way of convincing him that the first was real like repeating it; and if there lingered any doubt about the second, the father gave him yet a third. If, when the dream of old was doubled, the interpretation was sure, these repeated kisses left no room for doubt. The father renewed the tokens of his love that his son might be fully assured of his reality.

He did it that in the future it might never be questioned. Some of us were brought so low before we were converted, that God gave us an excess of joy when He saved us, that we might never forget it. Sometimes the devil says to me, “You are no child of God.” I have long ago given up answering him, for I found that it is a waste of time to argue with such a crafty old liar as he is; he knows too much for me. But if I must answer him, I say, “Why, I remember when I was saved by the Lord! I can never forget even the very spot of ground where first I saw my Saviour; there and then my joy rolled in like some great Atlantic billow, and burst in a mighty foam of bliss, covering all things. I cannot forget it.” That is an argument which even the devil cannot answer, for he cannot make me believe that such a thing never happened. The Father kissed me much, and I remember it full well. The Lord gives to some of us a clear deliverance such a bright, sunshiny day at our conversion, that henceforth we cannot question our state before Him, but must believe that we are eternally saved. ~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/2236.cfm