Here Aragorn pledges enduring loyalty to Frodo’s choice and quest. Frodo ‘knows’ Aragorn would have followed him to Mordor and so do we. We are positioned almost behind Frodo and we can see the tangible sincerity in Aragorn as Frodo does. This image tells us a lot about the reality of fellowship, the truth of a real promise and the unshakeable bond between the good. The image also provides a lot of information about how these qualities contrast those that lead to temptation.
See how Aragorn is absolutely present to Frodo. He holds eye contact and has placed himself slightly below the Hobbit’s eyeline so that he looks up into the eyes of the ringbearer. The aspect is of respect and veneration.
The manner of Aragorn’s eyes give his pledge to Frodo a real and tangible quality. His gaze is held and is focussed. Compare this with the gaze of Boromir when he first sees the ring.
There is something both held back and distant in Boromir. Boromir’s gaze tells us that he is both in the past and dreaming of a future. He is not present. The eyes of Boromir are filled with a darkness.
The eyes of Aragorn and the whole composition of the figure tells us of his presence and sincerity. Aragorn has mastered temptation here. He is master of himself and servant of the quest.
Aragorn is placing himself below Frodo but he inclines slightly toward the hobbit, projecting his sincerity while holding hands back towards his heart.
See that the hands are drawn back over Aragorn's heart, the fists being drawn together so that they themselves make a heart like shape. This demonstrates to Frodo that Aragorn is speaking from the heart and has subjugated any threat from himself. Hand to hand is heart to heart. Here we see the heart of the fellowship which has survived the breaking.
The resolution of this is that Frodo and Aragorn are unified. We see this in the mirror expressions of the hobbit and the king.
By folding Frodo's hand around the ring Aragorn makes a gesture which connects with the wider symbolism of hands in Fellowship. Closing hands signal gathering courage. See that the quality of Aragorn's hand on Frodo's is warm, gentle and encouraging. It is both guiding and soothing. In the contact there is also a sincere insistence to continue the quest. The hand makes a gentle 'push' in this direction. Frodo would certainly be aware that the heart of the Fellowship is intact.