(a) God appeared to Abram and told him to obey Him and be blameless. He would multiply him exceedingly, make him father of a multitude of nations and establish His covenant with him and his descendants. God also promised that Abram would possess the whole land of Canaan. The covenant involved the circumcision of all Abram's male children and Abram himself. It would be the great sign of the covenant for him and his descendants after him.
The circumcision was to extend to Abram's slaves and resident aliens. Any uncircumcised male should be cut off for breaking the covenant. Sarai's name was changed to Sarah and Abram's to Abraham. Sarai was to be blessed with a son. She would be the mother of many nations and kings would come from her. The promised child was to be named Isaac through whose descendants God would establish His covenant. As for Ishmael, God would bless him and multiply him as he would be father of twelve princes.

(b) Lessons to be learnt from the events are that:
(i) Obedience to God attracts God's blessings.
(ii) A lot of things, which look impossible to us, are possible with God (Abram and Sarah would bear a son after 100 years and 90 years, respectively).
(iii) We should believe God to fulfill His promises to us as children and descendants of Abraham.
(iv) Names have significance which affect us as individuals.