YHWH has organised His relationship with His people with covenants.

Some of these were implicit, e.g. in the Garden YWHW provided Adam and Woman everything that they needed - security, food, protection, communion. He expected Adam to do a few things, i.e. to obey not to eat of the tree, to procreate, to look after the garden. There was also a penalty clause - which proven very serious, destructive and having had a devastating effect on man since it was activated.

The covenant to Noah was unconditional. Just from YHWH's side.

However, the covenants with the Fathers of Israel had both unconditional and conditional elements. 

The Old Covenant that YHWH made with Israel at Sinai was very specific. If had magnificent promises and blessings. But it also had serious and dangerous penalty clauses. Just study the history of Israel to quickly realise how severe this can be on a people - thinking about the disasters that hit them before they were removed to other countries. And it is a very emotional thing to read what Josefus had to say about the fall of Jerusalem in 70AD.

The New Covenant, which has Yeshua as centre, are very different from the old. The old had much about works, the new is more about being. If one's character has been renewed - then one's works are also in line.

This is about the New Covenant, what are the origins, what are it terms.  It is not about just inviting Jesus into one's heart... There are many things that one has to learn and imprint on one's mind.