A.T. Robertson Commentary Colossians 1:5

"because of the hope which is laid up for you in the heavens, whereof ye heard before in the word of the truth of the gospel," — Colossians 1:5 (ASV)

Because of the hope (δια την ελπιδα). See Ro 8:24. It is not clear whether this phrase is to be linked with ευχα ιστουμεν at the beginning of verse 3 or (more likely) with την αγαπην just before. Note also here πιστις (faith), αγαπη (love), ελπις (hope), though not grouped together so sharply as in 1 Corinthians 13:13. Here hope is objective, the goal ahead.

Laid up (αποκειμεινην). Literally, "laid away or by." Old word used in Lu 19:20 of the pound laid away in a napkin. See also αποθησαυριζω, to store away for future use (1 Timothy 6:19). The same idea occurs in Mt 6:20 (treasure in heaven) and 1 Peter 1:4 and it is involved in Phm 3:20.

Ye heard before (προηκουσατε). First aorist indicative active of this old compound προακουω, though only here in the N.T. Before what? Before Paul wrote? Before the realization? Before the error of the Gnostics crept in? Each view is possible and has advocates. Lightfoot argues for the last and it is probably correct as is indicated by the next clause.

In the word of the truth of the gospel (εν τω λογω της αληθειας του ευαγγελιου). "In the preaching of the truth of the gospel" (Galatians 2:5,14) which is come (παροντος, present active participle agreeing with ευαγγελιου, being present, a classical use of παρειμ as in Ac 12:20). They heard the pure gospel from Epaphras before the Gnostics came.