Isaiah 56:7b For my house shall be called a house of prayer for all peoples.
Isaiah was telling that God wanted all people of all nations to join together and serve him. Not just people in Israel, but everyone. At the time, the people of Israel thought they were the only ones God accepted, and here is he putting them straight. He specifically draws attention to foreigners and eunuchs, that if they hold obedience to the word, he will receive them.
Back in the time of Moses, eunuchs were not allowed to be admitted into the community (Deut. 23:1) specifically because they could not procreate. There were also specific rules about people from certain places outside of the Israelites who could not join because of previous unkind things done to the Israelites. But here, God is saying that anyone who “observes the sabbaths and choose what pleases me” will be blessed by God.
Our God is a god for all. He wants to be THE God for all those who choose to follow him. If people are willing to lay down their worldly beliefs and follow God’s law, no matter their background, God wants to welcome them into his own. And through Jesus’s death and resurrection, we have the ability to be forgiven for our past sins, no matter what they are, as long as we truly want to repent. And that, my friends, is proof that our God, the one God is awesome.