was Abraham obedient?

5 Because that Abraham obeyed my voice, and kept my charge, my commandments, my statutes, and my laws.

And yet he had multiple wives and concubines. How is this keeping God's charge, commandments, statutes and laws?

Abraham had Sarah only as his wife, until Sarah persuaded him to take Hagar to produce a child.
Gen. 25: 1-6 After Sarah's death Abraham married Keturah and had children with her(looks like 6 sons)That is fine BUT
Verse 6 of Gen.25 talks of Abraham's concubines. Surely he would not consider Keturah as one of the concubines.
Abraham lived till he was 175. Isaac was born when he was 101 Gen.17:17, 21
No wander Isaac pined so much for his mother, he was 36 when she died and his father soon had a new wife. Isaac would have not received all the attention that he was used to

Abraham was 100 years old when Isaac was born:

Gen. 21:5 "And Abraham was an hundred years old, when his son Isaac was born unto him."

The expression "next year" in gn 17:21 does not necessarily mean that it would take one year for Isaac to be born, a normal pregnancy last 40 weeks (9 months). Abraham was 99 years when he received the promise and also, after that, he circumcised Ishmael and himself:

Gen. 17:23 And Abraham took Ishmael his son, and all that were born in his house, and all that were bought with his money, every male among the men of Abraham’s house; and circumcised the flesh of their foreskin in the selfsame day, as God had said unto him.
Gen. 17:24 And Abraham was ninety years old and nine, when he was circumcised in the flesh of his foreskin.