What Amirah should Hashem establish for him?
Rashi: What He promised to him [Radak - to establish the kingship to his sons after him].
Radak citing Ibn Ezra: It is a decree from Shamayim.
What is the meaning of "Asher l'Yir'asecha"?
Rashi: That I and my seed should fear Your name. You promised to me on this condition - "Im Yishmeru Vanecha Es Darkam" (Melachim I, 2:4).
Radak: To those who will cling to fear of You. The promise was to them.
Radak citing Ibn Ezra: Fulfill every decree that will bring me to fear You.
Malbim: Even though I request that my intent in Avodah not be for reward and Batza, I require that You fulfill Your promise for the kingship and all the goods, for fear of You. They will be the cause of fear of You - "Yere'echa Yir'uni v'Yismachu" (74). When they see that You bless a Tzadik, and fulfill the Bris and Chesed to those who fear You, they will fear You.