Commentary for Genesis 50:5

אשר כריתי לי means according to its plain sense “[the grave] which I have digged” just as (Exodus 21:33) “If a man shall dig (יכרה)”. There is a Midrashic explanation (Sotah 13a) which fits in with a meaning of the word כריתי, viz., אשר כריתי means אשר קניתי “which I have bought”. For R. Akiba said, “when I went to the coast-towns I heard them use for what we term מכירה “trading” the term כירה (Rosh Hashanah 26a). Another Midrashic explanation takes כריתי to be connected with כרי a piled up heap of grain, for Jacob had taken all the silver and gold which he had brought from the house of Laban and made a pile of it and said to Esau, “Take this for your share in the cave” (Midrash Tanchuma, Vayechi 6).

ואשובה. He (Pharaoh) should not worry that I would leave his country permanently.

השביעני לאמור, "has made me swear by saying, etc." Our sages in Sotah 36 have explained that Joseph used the word לאמור to forestall Pharaoh suggesting that Joseph have his oath voided. Joseph threatened that if this were possible, he would also have his oath not to reveal that Pharaoh did not understand Hebrew voided at the same time. The plain meaning is simply that inasmuch as Joseph described only the content of the oath, not its actual wording, he had to use the word לאמור.

Related to כרי דגור... כרי is Hebrew, and דגור is Aramaic.

A more homiletical approach would be this. Joseph wanted to head off Pharaoh's question why he had not consulted with him before swearing an oath which he could not keep without obtaining Pharaoh's consent. Joseph explained that there had not been time for such consultations as the oath had been sworn close to the time of Jacob's death. He indicated this by quoting his father as saying: "here I am about to die" (48,21). We have already discussed this in connection with 47,29.