In The Merchant of Venice, Shakespeare begins establishing the theme concerning the strength and devotion of Antonio's and Bassanio's friendship in the very first scene.
In the first scene, we learn that Antonio is feeling blue and worried because he has investments in ships that are presently sailing in troubled waters, as we learn when Solanio comments to Antonio that if he, Solanio, were out there with those ships, "the better part of [his] affections would / Be with my hopes" for their safe homecoming (I.i.15-16). When Bassanio enters the scene, we also learn that Bassanio owes Antonio a great deal of money he will not yet be able to repay. However, he discloses to Antonio his plans to court a wealthy woman who, if he marries, will solve all of his financial problems, enabling him to repay his friend Antonio. Trouble is, Bassanio will need to borrow more money from Antonio to be able to compete in courting her.
What's fascinating about this scene is just how lovingly and compassionately Antonio responds to Bassanio when the later speaks of his plight and how generously Antonio offers anything he can to Bassanio in order to help him, including his friendship, his services, and even more money:
And, if it stands, as you yourself still do,
Within the eye of honour, be assur'd,
My purse, my person, my extremest means,
Lie all unlock'd to your occasions. (141-44)
In saying "if it stands as you yourself still do, / Within the eye of honour," Antonio is asking Bassanio to tell him all about the lady and Bassanio's plans for wooing her and saying that if the plan is as honorable as Bassanio is still honorable, then Antonio will gladly do all he can to help him. In other words, Antonio is taking the opportunity to call Bassanio honorable despite his financial difficulties and the money he still owes Antonio.
Hence, all in all, Shakespeare establishes the theme of devoted friendship that is carried throughout the rest of the play, even to the extent that it looks like Antonio will have to lay down his life for Bassanio.