What is the meaning of Abraham laughing in Genesis 17.7? Is it the laughter of doubt and unbelief?
The word "laughed" really means "was joyful" and therefore cannot possibly convey the idea that Abraham laughed in unbelief at the promise of God to Him. On Abraham's part it was the laughter of faith and joyful worship. We may compare with this the Lord's words in John 8.56: "Abraham rejoiced to see my day: and he saw it, and was glad". In contrast to Abraham, Sarah's laughter in Genesis 18.12 was within herself. This was the laughter of unbelief, for in v.15 the Lord reproved her for laughing, which she denied out of fear, and had to be corrected by the Lord.
In Genesis 21.6 we have the laughter of faith on Sarah's part, for she said that God had made her to laugh. In Hebrews 11.11 it says that "Through faith also Sara herself received strength to conceive seed". It is very likely Sarah received the reproof and grasped, in earnest faith, at the same time the promise of Genesis 18.10-14. There does not seem to be any other specific time between the promise in Genesis 18 and the birth in Genesis 21 of Isaac, indicated in the Scriptures, when she believed the promise.
These references to laughter in the book of Genesis are interesting and, rightly understood, will give us practical lessons for our own lives. It is sadly true that there are many unbelieving believers, but God is looking for our faith in His Word and promises. In Genesis 18.12-15 Sarah was guilty of unbelief in a promise. In Mark 16 the disciples were guilty of unbelief in a fact (the resurrection of Christ). Three times over the Lord had to rebuke the disciples for their unbelief in a reality. Our God is the God of the impossible. Let us have faith in Him.
-John J Stubbs
What is the significance of the alternate names Jacob and Israel in the same verse, quite frequently in the Psalms (e.g. Ps 105.10) and other Scriptures, even when there seems to be no conflict between natural and spiritual?
We call to mind that occasion when "there wrestled a man" (Gen 32.24) with Jacob; this was one of the "theophanies", a pre-incarnate appearance of God Himself. The question was posed, "What is thy name? And he said, Jacob (i.e. supplanter). And he said, Thy name shall be called no more Jacob, but Israel" (Gen 32.27-28). Israel means "one who fights victoriously with God"; it has also been rendered "a prince with God". Subsequently, at Bethel, God reaffirmed and brought home to Jacob that he now had a new name, Israel (Gen 35.10).
In Scripture, a change of name signifies a change or development in character or status. The name Jacob is used of the natural Jacob, whereas Israel is used of the spiritual Jacob. These names are frequently given to the nation which stemmed from this grandson of Abraham. Thus we read, "it is even the time of Jacob's trouble" (Jer 30.7), the reference being to those future tribulation days. Then again, "blindness in part is happened to Israel, until the fulness of the Gentiles be come in" (Rom 11.25); it has not affected the whole nation, only the unbelieving part. However, that blindness is temporary, it will continue until the last Gentile is saved in this present age of grace.
Jacob (as a person) is never directly addressed as Israel either by God or man. In the years that followed his name change, we do not read of God addressing him directly, except on one occasion. There it is said that "God spake unto Israel in the visions of the night", but actually his attention was arrested by the repetition of his former name, "Jacob, Jacob" (Gen 46.2).
As to the verse(s) particularly cited in the question, we read, "Which covenant he made with Abraham, and his oath unto Isaac; and confirmed the same unto Jacob for a law, and to Israel for an everlasting covenant" (Ps 105.9-10), and it is clear that the reference is to the patriarchs themselves. Jacob, in his dream (Gen 28.10-15) received a pledge that the Lord's dealings with him would be in accordance with His covenant. When God changed Jacob's name to Israel, He did not change His covenant, for we read, "he blessed him there" (Gen 32.29) and it was with the former blessing according to His unchangeable word, hence the statement in Psalm 105.10.
-David E West