How does the father's reply to the elder brother apply to Israel's covenant promises?
The father's reply to the elder brother illustrates Israel's national standing under the covenant promises. Israel was under those promises nationally, and had they believed what God wanted them to believe, they could have enjoyed all the promises. Their self-righteous attitude, however, prevented that enjoyment.
Les explains that the father's words to the elder brother—"Son thou art ever with me, and all that I have is thine"—picture Israel's national position. Israel was under the covenant promises nationally; if they had come and believed what God wanted them to believe, they could have enjoyed all the promises. But their self-righteous attitude, like the elder brother's, meant it could never happen.