Let's start with Sarah vs. Keturah: Sarah lived to be 127...died in Canaan...all recorded in Genesis 23:1-2, 19-20. When does Keturah enter the picture in recorded Scripture?
We know Abraham took Keturah as a "wife" in Gen. 25:1 post Sarah's death...So, yet again, your monogamy timing is less than impeccable. As for Masek, indications from the Septuagint are that she was a maidservant...and some think perhaps Keturah's maidservant.
Per from what I could research in a limited amount of time, I didn't see Masek ever referenced as Abraham's wife. If she indeed was Keturah's maidservant, then likewise she came along after Sarah's death.
A possibility exists that Masek was a concubine...but even that isn't clearly delineated. And again, do you know how long Keturah lived? (I don't); so again, we don't know exact timing details of Abraham's matrimony, do we?
And why not? That was indeed a faithless action!
Certainly the whole thing was an act of faithlessness. Sarai didn't trust God's promise. She resorted to earthly means. The result was the people group that led to the Muslim break-out upon the earth...and neither Moses (Gen. 21) nor the apostle Paul (Gal. 4) speak positively of the consequences.
A. Hagar was gone from the scene by Gen. 21:14ff...so she wasn't in any relationship with Abraham when Keturah came along.
B. She was NEVER the maidservant of Abraham -- only Sarah (Sarai).
C. Most importantly, follow the following eye-witness testimony trail from the Bible:
(1) God never told Abraham to sleep with Hagar for a night. The Angel of the Lord--whom most commentators think is the pre-incarnated Son of God, told Hagar post sleepover to return to her mistress (mistress is a female master, in this case Sarai) and to submit to mistress Sarai. (He NEVER said to return to "your husband, Abram"...see Genesis 16).
(2) Hagar, even after sleeping with Abram once (that's all that's mentioned) continues to be labeled as a servant/slave by none other than…
…Abram,
…Sarai,
…the Angel of the Lord (who some say is the pre-incarnated Son of God),
…Moses (Gen. 25),
…even the apostle Paul (Gal. 4:21-31),
…and Hagar herself.
Sarai labels Hagar as a gift as a "wife" to Abram, but I question if a woman has the authority to "consent" on behalf of a slave.
Hagar was considered a slave both "before" and "after" sleeping with Abram. Why does the "before" matter? Just as a minor cannot "consent" to sex, a slave is in no better situation to "consent" to--or deny--her master's commands for sex with her husband. And in this case, the command didn't come from her husband, Abram; it came from her mistress (female word for "master"), Sarai (Sarai is twice referenced as "mistress"--Gen. 16:4,8).
Why does the "after" matter?
Because it shows she didn't become a "transformed" person--from slave to wifely status! Gen. 16:6,8,9; 21:11; 25:12; and Gal. 4:21-31 all are still referencing her as either a "slave" (twice in 21:11), "servant," or one who was told by the Angel to submit to her mistress (female word for "master"). By Gen. 25, Abraham is married to Keturah with no mention of Hagar (25:1) and is then buried with Sarah (25:10).
So, if we were to call all the key witnesses to the stand, and hear what they have to say:
Q Hagar, after Sarai gave you to Abram and Ishmael was conceived, did you still acknowledge Sarai as your "mistress" in your conversation with the Angel of the Lord? [female master]
A Yes. (Gen. 16:8)
Q Sarai, when you were in your early nineties when Isaac was a toddler, how did you characterize Hagar?
A I told Abraham, Get rid of thatslave woman and her son, for that slave woman's son will never share in the inheritance with my son, Isaac. (Gen. 21:10)
Q Abraham, after Sarah gave you Hagar and you slept with her, how did you characterize Hagar?
A I told Sarah, as mistress (master) of her servant, Your servant is in your hands. Do with her whatever you think best. (Gen. 16:6)
Q When Sarah began to mistreat her servant, Hagar, did you intervene like what we might expect a husband to do?
A No. Hagar was Sarah's servant.
Q Angel of the Lord, when you called to Hagar after she conceived Ishmael, how did you reference her?
A Servant of Sarai (Gen. 16:8)
Q And when you conversed with Hagar, did you, Angel of the Lord, acknowledge that she was released from her servant role to Sarai?
A No. In fact, I told her Go back to your mistress and submit to her. (Gen. 16:9)
Q Moses, since you wrote Genesis, how did you identify Hagar in her last reference of that book? Did you link her to Abraham?
A No. I identified her as "Sarah's maidservant" (Gen. 25:12).
Q So in that same passage, you link Ishmael to Abraham, but you link Hagar only to Sarah?
A Yes.
Q Apostle, Paul How did the Holy Spirit lead you to interpret the Old Covenant as expressed through Abraham?
A
For it is written that Abraham had two sons, one by the slave woman and the other by the free woman. His son by the slave woman was born in the ordinary way; but his son by the free woman was born as the result of a promise. These things may be taken figuratively, for the women represent two covenants. One covenant is from Mount Sinai and bears children who are to be slaves: This is Hagar. Now Hagar stands for Mount Sinai in Arabia and corresponds to the present city of Jerusalem, because she is in slavery with her children. But the Jerusalem above is free, and she is our mother...Now you brothers, like Isaac, are children of promise. At that time the son born in the ordinary way persecuted the son born by the power of the Spirit. It is the same now. But what does the Scripture say? 'Get rid of the slave woman and her son, for the slave woman's son will never share in the inheritance with the free woman's son.' Therefore, brothers, we are not children of the slave woman, but of the free woman. (Gal. 4:21-31)
2 wives and 2 handmaidens didn’t fit the song as well. So, according to you, Abraham was just sleeping with the help but only a one night stand so it doesn’t count?
The bible says in Genesis 16
3 And Sarai Abram’s wife took Hagar her maid the Egyptian, after Abram had dwelt ten years in the land of Canaan, and gave her to her husband Abram to be his wife.
4 And he went in unto Hagar, and she conceived: and when she saw that she had conceived, her mistress was despised in her eyes.
Moses wrote this as a Prophet of God as scripture and called her a wife. Sarai didn’t write it and Moses is not quoting her. No matter what her other titles might be, Moses called her a wife of Abraham. Moses is writing a history and was not alive during these events.
According to the prophet Moses, the prophet Abraham was a polygamist even if just for one night